diff --git a/ledis/t_kv.go b/ledis/t_kv.go
index 116aa87..136772b 100644
--- a/ledis/t_kv.go
+++ b/ledis/t_kv.go
@@ -197,7 +197,7 @@ func (db *DB) Incr(key []byte) (int64, error) {
 	return db.incr(key, 1)
 }
 
-func (db *DB) IncryBy(key []byte, increment int64) (int64, error) {
+func (db *DB) IncrBy(key []byte, increment int64) (int64, error) {
 	return db.incr(key, increment)
 }
 
diff --git a/server/cmd_bit.go b/server/cmd_bit.go
index cebb8dc..8fdd678 100644
--- a/server/cmd_bit.go
+++ b/server/cmd_bit.go
@@ -196,7 +196,7 @@ func bexpireCommand(c *client) error {
 
 	duration, err := ledis.StrInt64(args[1], nil)
 	if err != nil {
-		return err
+		return ErrValue
 	}
 
 	if v, err := c.db.BExpire(args[0], duration); err != nil {
@@ -216,7 +216,7 @@ func bexpireatCommand(c *client) error {
 
 	when, err := ledis.StrInt64(args[1], nil)
 	if err != nil {
-		return err
+		return ErrValue
 	}
 
 	if v, err := c.db.BExpireAt(args[0], when); err != nil {
diff --git a/server/cmd_hash.go b/server/cmd_hash.go
index cb3d752..b705d17 100644
--- a/server/cmd_hash.go
+++ b/server/cmd_hash.go
@@ -91,7 +91,7 @@ func hincrbyCommand(c *client) error {
 
 	delta, err := ledis.StrInt64(args[2], nil)
 	if err != nil {
-		return err
+		return ErrValue
 	}
 
 	var n int64
@@ -230,7 +230,7 @@ func hexpireCommand(c *client) error {
 
 	duration, err := ledis.StrInt64(args[1], nil)
 	if err != nil {
-		return err
+		return ErrValue
 	}
 
 	if v, err := c.db.HExpire(args[0], duration); err != nil {
@@ -250,7 +250,7 @@ func hexpireAtCommand(c *client) error {
 
 	when, err := ledis.StrInt64(args[1], nil)
 	if err != nil {
-		return err
+		return ErrValue
 	}
 
 	if v, err := c.db.HExpireAt(args[0], when); err != nil {
diff --git a/server/cmd_kv.go b/server/cmd_kv.go
index 1f61f5e..f526045 100644
--- a/server/cmd_kv.go
+++ b/server/cmd_kv.go
@@ -116,10 +116,10 @@ func incrbyCommand(c *client) error {
 
 	delta, err := ledis.StrInt64(args[1], nil)
 	if err != nil {
-		return err
+		return ErrValue
 	}
 
-	if n, err := c.db.IncryBy(c.args[0], delta); err != nil {
+	if n, err := c.db.IncrBy(c.args[0], delta); err != nil {
 		return err
 	} else {
 		c.writeInteger(n)
@@ -136,7 +136,7 @@ func decrbyCommand(c *client) error {
 
 	delta, err := ledis.StrInt64(args[1], nil)
 	if err != nil {
-		return err
+		return ErrValue
 	}
 
 	if n, err := c.db.DecrBy(c.args[0], delta); err != nil {
@@ -211,7 +211,7 @@ func expireCommand(c *client) error {
 
 	duration, err := ledis.StrInt64(args[1], nil)
 	if err != nil {
-		return err
+		return ErrValue
 	}
 
 	if v, err := c.db.Expire(args[0], duration); err != nil {
@@ -231,7 +231,7 @@ func expireAtCommand(c *client) error {
 
 	when, err := ledis.StrInt64(args[1], nil)
 	if err != nil {
-		return err
+		return ErrValue
 	}
 
 	if v, err := c.db.ExpireAt(args[0], when); err != nil {
diff --git a/server/cmd_kv_test.go b/server/cmd_kv_test.go
index 4f3cf23..56b2022 100644
--- a/server/cmd_kv_test.go
+++ b/server/cmd_kv_test.go
@@ -137,3 +137,81 @@ func TestKVIncrDecr(t *testing.T) {
 		t.Fatal(n)
 	}
 }
+
+func TestErrorParams(t *testing.T) {
+	c := getTestConn()
+	defer c.Close()
+
+	if _, err := c.Do("get", "a", "b", "c"); err == nil || err.Error() != SErrCmdParams {
+		t.Fatalf("invalid err %v", err)
+	}
+
+	if _, err := c.Do("set", "a", "b", "c"); err == nil || err.Error() != SErrCmdParams {
+		t.Fatalf("invalid err %v", err)
+	}
+
+	if _, err := c.Do("getset", "a", "b", "c"); err == nil || err.Error() != SErrCmdParams {
+		t.Fatalf("invalid err %v", err)
+	}
+
+	if _, err := c.Do("setnx", "a", "b", "c"); err == nil || err.Error() != SErrCmdParams {
+		t.Fatalf("invalid err %v", err)
+	}
+
+	if _, err := c.Do("exists", "a", "b"); err == nil || err.Error() != SErrCmdParams {
+		t.Fatalf("invalid err %v", err)
+	}
+
+	if _, err := c.Do("incr", "a", "b"); err == nil || err.Error() != SErrCmdParams {
+		t.Fatalf("invalid err %v", err)
+	}
+
+	if _, err := c.Do("incrby", "a"); err == nil || err.Error() != SErrCmdParams {
+		t.Fatalf("invalid err %v", err)
+	}
+
+	if _, err := c.Do("decrby", "a"); err == nil || err.Error() != SErrCmdParams {
+		t.Fatalf("invalid err %v", err)
+	}
+
+	if _, err := c.Do("del"); err == nil || err.Error() != SErrCmdParams {
+		t.Fatal("invalid err of %v", err)
+	}
+
+	if _, err := c.Do("mset"); err == nil || err.Error() != SErrCmdParams {
+		t.Fatal("invalid err of %v", err)
+	}
+
+	if _, err := c.Do("mset", "a", "b", "c"); err == nil || err.Error() != SErrCmdParams {
+		t.Fatal("invalid err of %v", err)
+	}
+
+	if _, err := c.Do("mget"); err == nil || err.Error() != SErrCmdParams {
+		t.Fatal("invalid err of %v", err)
+	}
+
+	if _, err := c.Do("expire"); err == nil || err.Error() != SErrCmdParams {
+		t.Fatal("invalid err of %v", err)
+	}
+
+	if _, err := c.Do("expire", "a", "b"); err == nil || err.Error() != SErrValue {
+		t.Fatal("invalid err of %v", err)
+	}
+
+	if _, err := c.Do("expireat"); err == nil || err.Error() != SErrCmdParams {
+		t.Fatal("invalid err of %v", err)
+	}
+
+	if _, err := c.Do("expireat", "a", "b"); err == nil || err.Error() != SErrValue {
+		t.Fatal("invalid err of %v", err)
+	}
+
+	if _, err := c.Do("ttl"); err == nil || err.Error() != SErrCmdParams {
+		t.Fatal("invalid err of %v", err)
+	}
+
+	if _, err := c.Do("persist"); err == nil || err.Error() != SErrCmdParams {
+		t.Fatal("invalid err of %v", err)
+	}
+
+}
diff --git a/server/cmd_list.go b/server/cmd_list.go
index bc059ec..cafd824 100644
--- a/server/cmd_list.go
+++ b/server/cmd_list.go
@@ -87,7 +87,7 @@ func lindexCommand(c *client) error {
 
 	index, err := ledis.StrInt64(args[1], nil)
 	if err != nil {
-		return err
+		return ErrValue
 	}
 
 	if v, err := c.db.LIndex(args[0], int32(index)); err != nil {
@@ -111,12 +111,12 @@ func lrangeCommand(c *client) error {
 
 	start, err = ledis.StrInt64(args[1], nil)
 	if err != nil {
-		return err
+		return ErrValue
 	}
 
 	stop, err = ledis.StrInt64(args[2], nil)
 	if err != nil {
-		return err
+		return ErrValue
 	}
 
 	if v, err := c.db.LRange(args[0], int32(start), int32(stop)); err != nil {
@@ -166,7 +166,7 @@ func lexpireCommand(c *client) error {
 
 	duration, err := ledis.StrInt64(args[1], nil)
 	if err != nil {
-		return err
+		return ErrValue
 	}
 
 	if v, err := c.db.LExpire(args[0], duration); err != nil {
@@ -186,7 +186,7 @@ func lexpireAtCommand(c *client) error {
 
 	when, err := ledis.StrInt64(args[1], nil)
 	if err != nil {
-		return err
+		return ErrValue
 	}
 
 	if v, err := c.db.LExpireAt(args[0], when); err != nil {
diff --git a/server/cmd_zset.go b/server/cmd_zset.go
index e8e8014..8dc465e 100644
--- a/server/cmd_zset.go
+++ b/server/cmd_zset.go
@@ -29,7 +29,7 @@ func zaddCommand(c *client) error {
 	for i := 0; i < len(params); i++ {
 		score, err := ledis.StrInt64(args[2*i], nil)
 		if err != nil {
-			return err
+			return ErrValue
 		}
 
 		params[i].Score = score
@@ -104,7 +104,7 @@ func zincrbyCommand(c *client) error {
 
 	delta, err := ledis.StrInt64(args[1], nil)
 	if err != nil {
-		return err
+		return ErrValue
 	}
 
 	if v, err := c.db.ZIncrBy(key, delta, args[2]); err != nil {
@@ -444,7 +444,7 @@ func zexpireCommand(c *client) error {
 
 	duration, err := ledis.StrInt64(args[1], nil)
 	if err != nil {
-		return err
+		return ErrValue
 	}
 
 	if v, err := c.db.ZExpire(args[0], duration); err != nil {
@@ -464,7 +464,7 @@ func zexpireAtCommand(c *client) error {
 
 	when, err := ledis.StrInt64(args[1], nil)
 	if err != nil {
-		return err
+		return ErrValue
 	}
 
 	if v, err := c.db.ZExpireAt(args[0], when); err != nil {
diff --git a/server/const.go b/server/const.go
index 36235a8..9be33fa 100644
--- a/server/const.go
+++ b/server/const.go
@@ -8,6 +8,7 @@ var (
 	ErrEmptyCommand = errors.New("empty command")
 	ErrNotFound     = errors.New("command not found")
 	ErrCmdParams    = errors.New("invalid command param")
+	ErrValue        = errors.New("value is not an integer or out of range")
 )
 
 var (
@@ -16,6 +17,8 @@ var (
 	NullBulk  = []byte("-1")
 	NullArray = []byte("-1")
 
-	PONG = "PONG"
-	OK   = "OK"
+	PONG          = "PONG"
+	OK            = "OK"
+	SErrCmdParams = "ERR invalid command param"
+	SErrValue     = "ERR value is not an integer or out of range"
 )