diff --git a/model.go b/model.go
index 62da0ea4..e22a5c64 100644
--- a/model.go
+++ b/model.go
@@ -23,6 +23,10 @@ func (s *Orm) toModel(value interface{}) *Model {
 	return &Model{Data: value, driver: s.driver}
 }
 
+func (m *Model) PrimaryKey() string {
+	return "Id"
+}
+
 func (m *Model) Fields() (fields []Field) {
 	typ := reflect.TypeOf(m.Data).Elem()
 
@@ -33,7 +37,11 @@ func (m *Model) Fields() (fields []Field) {
 			field.Name = p.Name
 			field.DbName = toSnake(p.Name)
 			field.Value = reflect.ValueOf(m.Data).Elem().FieldByName(p.Name).Interface()
-			field.SqlType = getSqlType(m.driver, field.Value, 0)
+			if m.PrimaryKey() == p.Name {
+				field.SqlType = getPrimaryKeySqlType(m.driver, field.Value, 0)
+			} else {
+				field.SqlType = getSqlType(m.driver, field.Value, 0)
+			}
 			fields = append(fields, field)
 		}
 	}
diff --git a/orm.go b/orm.go
index 53d4aa24..ed8494f4 100644
--- a/orm.go
+++ b/orm.go
@@ -28,7 +28,7 @@ type Orm struct {
 func (s *Orm) setModel(model interface{}) (err error) {
 	s.Model = s.toModel(model)
 	s.TableName = s.Model.TableName()
-	s.PrimaryKey = "id"
+	s.PrimaryKey = s.Model.PrimaryKey()
 	return
 }
 
diff --git a/sql_type.go b/sql_type.go
index 6069967d..2f57ba1d 100644
--- a/sql_type.go
+++ b/sql_type.go
@@ -5,6 +5,27 @@ import (
 	"time"
 )
 
+func getPrimaryKeySqlType(adaptor string, column interface{}, size int) string {
+	switch adaptor {
+	case "mysql":
+		suffix_str := " NOT NULL AUTO_INCREMENT PRIMARY KEY"
+		switch column.(type) {
+		case int, int8, int16, int32, uint, uint8, uint16, uint32:
+			return "int" + suffix_str
+		case int64, uint64:
+			return "bigint" + suffix_str
+		}
+	case "postgres":
+		switch column.(type) {
+		case int, int8, int16, int32, uint, uint8, uint16, uint32:
+			return "serial"
+		case int64, uint64:
+			return "bigserial"
+		}
+	}
+	panic("unsupported sql adaptor, please submit an issue in github")
+}
+
 func getSqlType(adaptor string, column interface{}, size int) string {
 	switch adaptor {
 	case "mysql":
@@ -55,7 +76,7 @@ func getSqlType(adaptor string, column interface{}, size int) string {
 		default:
 			panic("invalid sql type")
 		}
+	default:
+		panic("unsupported sql adaptor, please submit an issue in github")
 	}
-
-	panic("unsupported sql adaptor, please submit an issue in github")
 }