diff --git a/char.go b/char.go
index 4d42e1f..3d65824 100644
--- a/char.go
+++ b/char.go
@@ -7,7 +7,7 @@ const (
 	CharDelete    = 4
 	CharLineEnd   = 5
 	CharForward   = 6
-	CharCannel    = 7
+	CharCancel    = 7
 	CharCtrlH     = 8
 	CharTab       = 9
 	CharCtrlJ     = 10
diff --git a/complete.go b/complete.go
new file mode 100644
index 0000000..4655946
--- /dev/null
+++ b/complete.go
@@ -0,0 +1,249 @@
+package readline
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+)
+
+type opCompleter struct {
+	w  io.Writer
+	op *Operation
+	ac AutoCompleter
+
+	inCompleteMode  bool
+	inSelectMode    bool
+	candicate       [][]rune
+	candicateSource []rune
+	candicateOff    int
+	candicateChoise int
+	candicateColNum int
+}
+
+func newOpCompleter(w io.Writer, op *Operation) *opCompleter {
+	return &opCompleter{
+		w:  w,
+		op: op,
+		ac: op.cfg.AutoComplete,
+	}
+}
+
+func (o *opCompleter) doSelect() {
+	if len(o.candicate) == 1 {
+		o.op.buf.WriteRunes(o.candicate[0])
+		o.ExitCompleteMode(false)
+		return
+	}
+	o.nextCandicate(1)
+	o.CompleteRefresh()
+}
+
+func (o *opCompleter) nextCandicate(i int) {
+	o.candicateChoise += i
+	o.candicateChoise = o.candicateChoise % len(o.candicate)
+	if o.candicateChoise < 0 {
+		o.candicateChoise = len(o.candicate) + o.candicateChoise
+	}
+}
+
+func (o *opCompleter) OnComplete() {
+	if o.IsInCompleteSelectMode() {
+		o.doSelect()
+		return
+	}
+
+	buf := o.op.buf
+	rs := buf.Runes()
+
+	if o.IsInCompleteMode() && EqualRunes(rs, o.candicateSource) {
+		o.EnterCompleteSelectMode()
+		o.doSelect()
+		return
+	}
+
+	o.ExitCompleteSelectMode()
+	o.candicateSource = rs
+	newLines, offset := o.ac.Do(rs, buf.idx)
+	if len(newLines) == 0 {
+		o.ExitCompleteMode(false)
+		return
+	}
+
+	// only Aggregate candicates in non-complete mode
+	if !o.IsInCompleteMode() {
+		if len(newLines) == 1 {
+			buf.WriteRunes(newLines[0])
+			o.ExitCompleteMode(false)
+			return
+		}
+
+		same, size := AggRunes(newLines)
+		if size > 0 {
+			buf.WriteRunes(same)
+			o.ExitCompleteMode(false)
+			return
+		}
+	}
+
+	o.EnterCompleteMode(offset, newLines)
+}
+
+func (o *opCompleter) IsInCompleteSelectMode() bool {
+	return o.inSelectMode
+}
+
+func (o *opCompleter) IsInCompleteMode() bool {
+	return o.inCompleteMode
+}
+
+func (o *opCompleter) HandleCompleteSelect(r rune) bool {
+	next := true
+	switch r {
+	case CharEnter, CharCtrlJ:
+		next = false
+		o.op.buf.WriteRunes(o.op.candicate[o.op.candicateChoise])
+		o.ExitCompleteMode(false)
+	case CharLineStart:
+		num := o.candicateChoise % o.candicateColNum
+		o.nextCandicate(-num)
+	case CharLineEnd:
+		num := o.candicateColNum - o.candicateChoise%o.candicateColNum - 1
+		o.candicateChoise += num
+		if o.candicateChoise >= len(o.candicate) {
+			o.candicateChoise = len(o.candicate) - 1
+		}
+	case CharBackspace:
+		o.ExitCompleteSelectMode()
+		next = false
+	case CharTab, CharForward:
+		o.doSelect()
+	case CharCancel, CharInterrupt:
+		o.ExitCompleteMode(true)
+		next = false
+	case CharNext:
+		tmpChoise := o.candicateChoise + o.candicateColNum
+		if tmpChoise >= o.getMatrixSize() {
+			tmpChoise -= o.getMatrixSize()
+		} else if tmpChoise >= len(o.candicate) {
+			tmpChoise += o.candicateColNum
+			tmpChoise -= o.getMatrixSize()
+		}
+		o.candicateChoise = tmpChoise
+	case CharBackward:
+		o.nextCandicate(-1)
+	case CharPrev:
+		tmpChoise := o.candicateChoise - o.candicateColNum
+		if tmpChoise < 0 {
+			tmpChoise += o.getMatrixSize()
+			if tmpChoise >= len(o.candicate) {
+				tmpChoise -= o.candicateColNum
+			}
+		}
+		o.candicateChoise = tmpChoise
+	default:
+		next = false
+	}
+	if next {
+		o.CompleteRefresh()
+		return true
+	}
+	return false
+}
+
+func (o *opCompleter) getMatrixSize() int {
+	line := len(o.candicate) / o.candicateColNum
+	if len(o.candicate)%o.candicateColNum != 0 {
+		line++
+	}
+	return line * o.candicateColNum
+}
+
+func (o *opCompleter) CompleteRefresh() {
+	if !o.inCompleteMode {
+		return
+	}
+	lineCnt := o.op.buf.CursorLineCount()
+	colWidth := 0
+	for _, c := range o.candicate {
+		w := RunesWidth(c)
+		if w > colWidth {
+			colWidth = w
+		}
+	}
+	colNum := getWidth() / (colWidth + o.candicateOff + 2)
+	o.candicateColNum = colNum
+	buf := bytes.NewBuffer(nil)
+	buf.Write(bytes.Repeat([]byte("\n"), lineCnt))
+	same := o.op.buf.RuneSlice(-o.candicateOff)
+	colIdx := 0
+	lines := 1
+	buf.WriteString("\033[J")
+	for idx, c := range o.candicate {
+		inSelect := idx == o.candicateChoise && o.IsInCompleteSelectMode()
+		if inSelect {
+			buf.WriteString("\033[30;47m")
+		}
+		buf.WriteString(string(same))
+		buf.WriteString(string(c))
+		buf.Write(bytes.Repeat([]byte(" "), colWidth-len(c)))
+		if inSelect {
+			buf.WriteString("\033[0m")
+		}
+
+		buf.WriteString("  ")
+		colIdx++
+		if colIdx == colNum {
+			buf.WriteString("\n")
+			lines++
+			colIdx = 0
+		}
+	}
+
+	// move back
+	fmt.Fprintf(buf, "\033[%dA\r", lineCnt-1+lines)
+	fmt.Fprintf(buf, "\033[%dC", o.op.buf.idx+o.op.buf.PromptLen())
+	o.w.Write(buf.Bytes())
+}
+
+func (o *opCompleter) aggCandicate(candicate [][]rune) int {
+	offset := 0
+	for i := 0; i < len(candicate[0]); i++ {
+		for j := 0; j < len(candicate)-1; j++ {
+			if i > len(candicate[j]) {
+				goto aggregate
+			}
+			if candicate[j][i] != candicate[j+1][i] {
+				goto aggregate
+			}
+		}
+		offset = i
+	}
+aggregate:
+	return offset
+}
+
+func (o *opCompleter) EnterCompleteSelectMode() {
+	o.inSelectMode = true
+	o.candicateChoise = -1
+	o.CompleteRefresh()
+}
+
+func (o *opCompleter) EnterCompleteMode(offset int, candicate [][]rune) {
+	o.inCompleteMode = true
+	o.candicate = candicate
+	o.candicateOff = offset
+	o.CompleteRefresh()
+}
+
+func (o *opCompleter) ExitCompleteSelectMode() {
+	o.inSelectMode = false
+	o.candicate = nil
+	o.candicateChoise = -1
+	o.candicateOff = -1
+	o.candicateSource = nil
+}
+
+func (o *opCompleter) ExitCompleteMode(revent bool) {
+	o.inCompleteMode = false
+	o.ExitCompleteSelectMode()
+}
diff --git a/example/main.go b/example/main.go
index bd380ef..c9199e6 100644
--- a/example/main.go
+++ b/example/main.go
@@ -1,9 +1,11 @@
 package main
 
 import (
+	"fmt"
 	"io"
 	"log"
 	"strconv"
+	"strings"
 	"time"
 
 	"github.com/chzyer/readline"
@@ -16,10 +18,30 @@ bye: quit
 `[1:])
 }
 
+type Completer struct {
+}
+
+func (c *Completer) Do(line []rune, pos int) (newLine [][]rune, off int) {
+	list := [][]rune{
+		[]rune("sayhello"), []rune("help"), []rune("bye"),
+	}
+	for i := 0; i <= 100; i++ {
+		list = append(list, []rune(fmt.Sprintf("com%d", i)))
+	}
+	line = line[:pos]
+	for _, r := range list {
+		if strings.HasPrefix(string(r), string(line)) {
+			newLine = append(newLine, r[len(line):])
+		}
+	}
+	return newLine, len(line)
+}
+
 func main() {
 	l, err := readline.NewEx(&readline.Config{
-		Prompt:      "\033[31m»\033[0m ",
-		HistoryFile: "/tmp/readline.tmp",
+		Prompt:       "\033[31m»\033[0m ",
+		HistoryFile:  "/tmp/readline.tmp",
+		AutoComplete: new(Completer),
 	})
 	if err != nil {
 		panic(err)
diff --git a/operation.go b/operation.go
index 27e013e..398f7ac 100644
--- a/operation.go
+++ b/operation.go
@@ -13,6 +13,7 @@ type Operation struct {
 
 	*opHistory
 	*opSearch
+	*opCompleter
 }
 
 type wrapWriter struct {
@@ -31,6 +32,9 @@ func (w *wrapWriter) Write(b []byte) (int, error) {
 	if w.r.IsSearchMode() {
 		w.r.SearchRefresh(-1)
 	}
+	if w.r.IsInCompleteMode() {
+		w.r.CompleteRefresh()
+	}
 	return n, err
 }
 
@@ -43,6 +47,7 @@ func NewOperation(t *Terminal, cfg *Config) *Operation {
 		opHistory: newOpHistory(cfg.HistoryFile),
 	}
 	op.opSearch = newOpSearch(op.buf.w, op.buf, op.opHistory)
+	op.opCompleter = newOpCompleter(op.buf.w, op)
 	go op.ioloop()
 	return op
 }
@@ -50,17 +55,41 @@ func NewOperation(t *Terminal, cfg *Config) *Operation {
 func (o *Operation) ioloop() {
 	for {
 		keepInSearchMode := false
+		keepInCompleteMode := false
 		r := o.t.ReadRune()
+
+		if o.IsInCompleteSelectMode() {
+			keepInCompleteMode = o.HandleCompleteSelect(r)
+			if keepInCompleteMode {
+				continue
+			}
+
+			o.buf.Refresh()
+			switch r {
+			case CharInterrupt, CharEnter, CharCtrlJ:
+				o.t.KickRead()
+				fallthrough
+			case CharCancel:
+				continue
+			}
+		}
+
 		switch r {
-		case CharCannel:
+		case CharCancel:
 			if o.IsSearchMode() {
 				o.ExitSearchMode(true)
 				o.buf.Refresh()
 			}
+			if o.IsInCompleteMode() {
+				o.ExitCompleteMode(true)
+				o.buf.Refresh()
+			}
 		case CharTab:
-			if o.cfg.AutoComplete == nil {
+			if o.opCompleter == nil {
 				break
 			}
+			o.OnComplete()
+			keepInCompleteMode = true
 		case CharBckSearch:
 			o.SearchMode(S_DIR_BCK)
 			keepInSearchMode = true
@@ -69,6 +98,7 @@ func (o *Operation) ioloop() {
 			keepInSearchMode = true
 		case CharKill:
 			o.buf.Kill()
+			keepInCompleteMode = true
 		case MetaNext:
 			o.buf.MoveToNextWord()
 		case CharTranspose:
@@ -87,8 +117,12 @@ func (o *Operation) ioloop() {
 			if o.IsSearchMode() {
 				o.SearchBackspace()
 				keepInSearchMode = true
-			} else {
-				o.buf.Backspace()
+				break
+			}
+
+			o.buf.Backspace()
+			if o.IsInCompleteMode() {
+				o.OnComplete()
 			}
 		case MetaBackspace, CharCtrlW:
 			o.buf.BackEscapeWord()
@@ -122,6 +156,12 @@ func (o *Operation) ioloop() {
 				o.ExitSearchMode(true)
 				break
 			}
+			if o.IsInCompleteMode() {
+				o.t.KickRead()
+				o.ExitCompleteMode(true)
+				o.buf.Refresh()
+				break
+			}
 			o.buf.MoveToLineEnd()
 			o.buf.Refresh()
 			o.buf.WriteString("^C\n")
@@ -130,13 +170,25 @@ func (o *Operation) ioloop() {
 			if o.IsSearchMode() {
 				o.SearchChar(r)
 				keepInSearchMode = true
-			} else {
-				o.buf.WriteRune(r)
+				break
+			}
+			o.buf.WriteRune(r)
+			if o.IsInCompleteMode() {
+				o.OnComplete()
+				keepInCompleteMode = true
 			}
 		}
 		if !keepInSearchMode && o.IsSearchMode() {
 			o.ExitSearchMode(false)
 			o.buf.Refresh()
+		} else if o.IsInCompleteMode() {
+			if !keepInCompleteMode {
+				o.ExitCompleteMode(false)
+				o.buf.Refresh()
+			} else {
+				o.buf.Refresh()
+				o.CompleteRefresh()
+			}
 		}
 		if !o.IsSearchMode() {
 			o.UpdateHistory(o.buf.Runes(), false)
diff --git a/readline.go b/readline.go
index 3bd5603..6da9267 100644
--- a/readline.go
+++ b/readline.go
@@ -8,7 +8,11 @@ type Instance struct {
 }
 
 type AutoCompleter interface {
-	Do(line []rune, pos int) (newLine []rune, newPos int, ok bool)
+	Do(line []rune, pos int) (newLine [][]rune, offset int)
+}
+
+type AutoCompleteHinter interface {
+	Hint(line []rune, pos int) ([]rune, bool)
 }
 
 type Config struct {
diff --git a/runebuf.go b/runebuf.go
index d19abc8..bae2862 100644
--- a/runebuf.go
+++ b/runebuf.go
@@ -28,8 +28,21 @@ func (r *RuneBuffer) PromptLen() int {
 	return RunesWidth(RunesColorFilter(r.prompt))
 }
 
+func (r *RuneBuffer) RuneSlice(i int) []rune {
+	if i > 0 {
+		rs := make([]rune, i)
+		copy(rs, r.buf[r.idx:r.idx+i])
+		return rs
+	}
+	rs := make([]rune, -i)
+	copy(rs, r.buf[r.idx+i:r.idx])
+	return rs
+}
+
 func (r *RuneBuffer) Runes() []rune {
-	return r.buf
+	newr := make([]rune, len(r.buf))
+	copy(newr, r.buf)
+	return newr
 }
 
 func (r *RuneBuffer) Pos() int {
@@ -67,7 +80,7 @@ func (r *RuneBuffer) WriteRune(s rune) {
 func (r *RuneBuffer) WriteRunes(s []rune) {
 	tail := append(s, r.buf[r.idx:]...)
 	r.buf = append(r.buf[:r.idx], tail...)
-	r.idx++
+	r.idx += len(s)
 	r.Refresh()
 }
 
diff --git a/utils.go b/utils.go
index 7e38b92..2870d59 100644
--- a/utils.go
+++ b/utils.go
@@ -228,3 +228,45 @@ func RunesWidth(r []rune) (length int) {
 	}
 	return
 }
+
+func AggRunes(candicate [][]rune) (same []rune, size int) {
+	for i := 0; i < len(candicate[0]); i++ {
+		for j := 0; j < len(candicate)-1; j++ {
+			if i >= len(candicate[j]) || i >= len(candicate[j+1]) {
+				goto aggregate
+			}
+			if candicate[j][i] != candicate[j+1][i] {
+				goto aggregate
+			}
+		}
+		size = i + 1
+	}
+aggregate:
+	if size > 0 {
+		same = CopyRunes(candicate[0][:size])
+		for i := 0; i < len(candicate); i++ {
+			n := CopyRunes(candicate[i])
+			copy(n, n[size:])
+			candicate[i] = n[:len(n)-size]
+		}
+	}
+	return
+}
+
+func CopyRunes(r []rune) []rune {
+	n := make([]rune, len(r))
+	copy(n, r)
+	return n
+}
+
+func EqualRunes(r, r2 []rune) bool {
+	if len(r) != len(r2) {
+		return false
+	}
+	for idx := range r {
+		if r[idx] != r2[idx] {
+			return false
+		}
+	}
+	return true
+}
diff --git a/utils_test.go b/utils_test.go
index 078bb17..de74175 100644
--- a/utils_test.go
+++ b/utils_test.go
@@ -1,14 +1,17 @@
 package readline
 
-import "testing"
+import (
+	"reflect"
+	"testing"
+)
 
-type Twidth struct {
+type twidth struct {
 	r      []rune
 	length int
 }
 
 func TestRuneWidth(t *testing.T) {
-	runes := []Twidth{
+	runes := []twidth{
 		{[]rune("☭"), 1},
 		{[]rune("a"), 1},
 		{[]rune("你"), 2},
@@ -20,3 +23,46 @@ func TestRuneWidth(t *testing.T) {
 		}
 	}
 }
+
+type tagg struct {
+	r      [][]rune
+	e      [][]rune
+	length int
+}
+
+func TestAggRunes(t *testing.T) {
+	runes := []tagg{
+		{
+			[][]rune{[]rune("ab"), []rune("a"), []rune("abc")},
+			[][]rune{[]rune("b"), []rune(""), []rune("bc")},
+			1,
+		},
+		{
+			[][]rune{[]rune("addb"), []rune("ajkajsdf"), []rune("aasdfkc")},
+			[][]rune{[]rune("ddb"), []rune("jkajsdf"), []rune("asdfkc")},
+			1,
+		},
+		{
+			[][]rune{[]rune("ddb"), []rune("ajksdf"), []rune("aasdfkc")},
+			[][]rune{[]rune("ddb"), []rune("ajksdf"), []rune("aasdfkc")},
+			0,
+		},
+		{
+			[][]rune{[]rune("ddb"), []rune("ddajksdf"), []rune("ddaasdfkc")},
+			[][]rune{[]rune("b"), []rune("ajksdf"), []rune("aasdfkc")},
+			2,
+		},
+	}
+	for _, r := range runes {
+		same, off := AggRunes(r.r)
+		if off != r.length {
+			t.Fatal("result not expect", off)
+		}
+		if len(same) != off {
+			t.Fatal("result not expect", same)
+		}
+		if !reflect.DeepEqual(r.r, r.e) {
+			t.Fatal("result not expect")
+		}
+	}
+}