diff --git a/core/codes/codes.go b/core/codes/codes.go
new file mode 100644
index 00000000..77f59220
--- /dev/null
+++ b/core/codes/codes.go
@@ -0,0 +1,14 @@
+package codes
+
+// A Code is an unsigned 32-bit error code as defined in the beego spec.
+type Code uint32
+
+const (
+	// SessionSessionStartError means func SessionStart error in session module.
+	SessionSessionStartError Code = 5001001
+)
+
+// CodeToStr is a map about Code and Code's message
+var CodeToStr = map[Code]string{
+	SessionSessionStartError : `"SESSION_MODULE_SESSION_START_ERROR"`,
+}
\ No newline at end of file
diff --git a/core/error/error.go b/core/error/error.go
new file mode 100644
index 00000000..6caf9839
--- /dev/null
+++ b/core/error/error.go
@@ -0,0 +1,53 @@
+package error
+
+import (
+	"fmt"
+	"github.com/beego/beego/v2/core/codes"
+	"strconv"
+)
+
+// Error type defines custom error for Beego. It is used by every module
+// in Beego. Each `Error` message contains three pieces of data: error code,
+// error message.
+// More docs http://beego.me/docs/module/error.md.
+type Error struct {
+    Code codes.Code
+    Msg string
+}
+
+// New returns a Error representing c and msg.
+func New(c codes.Code, msg string) *Error {
+    return &Error{Code: c, Msg: msg}
+}
+
+// Err returns an error representing c and msg.  If c is OK, returns nil.
+func Err(c codes.Code, msg string) error {
+	return New(c, msg)
+}
+
+// Errorf returns Error(c, fmt.Sprintf(format, a...)).
+func Errorf(c codes.Code, format string, a ...interface{}) error {
+	return Err(c, fmt.Sprintf(format, a...))
+}
+
+// Error returns formatted message for user.
+func (e *Error) Error() string {
+	codeSrt := strconv.FormatUint(uint64(e.GetCode()), 10)
+	return fmt.Sprintf("beego error: code = %s desc = %s", codeSrt, e.GetMessage())
+}
+
+// GetCode returns Error's Code.
+func (e *Error) GetCode() codes.Code {
+	if e != nil {
+		return e.Code
+	}
+	return 0
+}
+
+// GetMessage returns Error's Msg.
+func (e *Error) GetMessage() string {
+	if e != nil {
+		return e.Msg
+	}
+	return ""
+}
\ No newline at end of file
diff --git a/core/error/error_test.go b/core/error/error_test.go
new file mode 100644
index 00000000..630b277c
--- /dev/null
+++ b/core/error/error_test.go
@@ -0,0 +1,152 @@
+package error
+
+import (
+	"github.com/beego/beego/v2/core/codes"
+	"reflect"
+	"testing"
+)
+
+func TestErr(t *testing.T) {
+	type args struct {
+		c   codes.Code
+		msg string
+	}
+	tests := []struct {
+		name    string
+		args    args
+		wantErr bool
+	}{
+		// TODO: Add test cases.
+		{name: "1", args: args{codes.SessionSessionStartError, codes.CodeToStr[codes.SessionSessionStartError]}, wantErr: true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if err := Err(tt.args.c, tt.args.msg); (err != nil) != tt.wantErr {
+				t.Errorf("Err() error = %v, wantErr %v", err, tt.wantErr)
+			}
+		})
+	}
+}
+
+func TestError_Error(t *testing.T) {
+	type fields struct {
+		Code codes.Code
+		Msg  string
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		want   string
+	}{
+		// TODO: Add test cases.
+		{name: "1", fields: fields{codes.SessionSessionStartError, codes.CodeToStr[codes.SessionSessionStartError]}, want: "beego error: code = 5001001 desc = \"SESSION_MODULE_SESSION_START_ERROR\""},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			e := &Error{
+				Code: tt.fields.Code,
+				Msg:  tt.fields.Msg,
+			}
+			if got := e.Error(); got != tt.want {
+				t.Errorf("Error() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestError_GetCode(t *testing.T) {
+	type fields struct {
+		Code codes.Code
+		Msg  string
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		want   codes.Code
+	}{
+		// TODO: Add test cases.
+		{name: "1", fields: fields{codes.SessionSessionStartError, codes.CodeToStr[codes.SessionSessionStartError]}, want: codes.SessionSessionStartError},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			e := &Error{
+				Code: tt.fields.Code,
+				Msg:  tt.fields.Msg,
+			}
+			if got := e.GetCode(); got != tt.want {
+				t.Errorf("GetCode() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestError_GetMessage(t *testing.T) {
+	type fields struct {
+		Code codes.Code
+		Msg  string
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		want   string
+	}{
+		// TODO: Add test cases.
+		{name: "1", fields: fields{codes.SessionSessionStartError, codes.CodeToStr[codes.SessionSessionStartError]}, want: codes.CodeToStr[codes.SessionSessionStartError]},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			e := &Error{
+				Code: tt.fields.Code,
+				Msg:  tt.fields.Msg,
+			}
+			if got := e.GetMessage(); got != tt.want {
+				t.Errorf("GetMessage() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestErrorf(t *testing.T) {
+	type args struct {
+		c      codes.Code
+		format string
+		a      []interface{}
+	}
+	tests := []struct {
+		name    string
+		args    args
+		wantErr bool
+	}{
+		// TODO: Add test cases.
+		{name: "1", args: args{codes.SessionSessionStartError, "%s", []interface{}{codes.CodeToStr[codes.SessionSessionStartError]}}, wantErr: true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if err := Errorf(tt.args.c, tt.args.format, tt.args.a...); (err != nil) != tt.wantErr {
+				t.Errorf("Errorf() error = %v, wantErr %v", err, tt.wantErr)
+			}
+		})
+	}
+}
+
+func TestNew(t *testing.T) {
+	type args struct {
+		c   codes.Code
+		msg string
+	}
+	tests := []struct {
+		name string
+		args args
+		want *Error
+	}{
+		// TODO: Add test cases.
+		{name: "1", args: args{codes.SessionSessionStartError, codes.CodeToStr[codes.SessionSessionStartError]}, want: &Error{Code:codes.SessionSessionStartError,  Msg:codes.CodeToStr[codes.SessionSessionStartError]}},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := New(tt.args.c, tt.args.msg); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("New() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}