diff --git a/cdc/sink/codec/avro.go b/cdc/sink/codec/avro.go
index fa6f004ef26..bc6c80c8f7f 100644
--- a/cdc/sink/codec/avro.go
+++ b/cdc/sink/codec/avro.go
@@ -24,6 +24,7 @@ import (
 	"strconv"
 	"time"
 
+	"github.com/linkedin/goavro/v2"
 	"github.com/pingcap/errors"
 	"github.com/pingcap/log"
 	"github.com/pingcap/tidb/parser/mysql"
@@ -227,11 +228,11 @@ func ColumnInfoToAvroSchema(name string, columnInfo []*model.Column) (string, er
 		}
 		field := make(map[string]interface{})
 		field["name"] = col.Name
-		if col.Flag.IsHandleKey() {
-			field["type"] = avroType
-		} else {
+		if col.Flag.IsNullable() {
 			field["type"] = []interface{}{"null", avroType}
 			field["default"] = nil
+		} else {
+			field["type"] = avroType
 		}
 
 		top.Fields = append(top.Fields, field)
@@ -256,13 +257,12 @@ func rowToAvroNativeData(cols []*model.Column, colInfos []rowcodec.ColInfo, tz *
 			return nil, err
 		}
 
-		if col.Flag.IsHandleKey() {
+		// https://pkg.go.dev/github.com/linkedin/goavro/v2#Union
+		if col.Flag.IsNullable() {
+			ret[col.Name] = goavro.Union(str, data)
+		} else {
 			ret[col.Name] = data
-			continue
 		}
-		union := make(map[string]interface{}, 1)
-		union[str] = data
-		ret[col.Name] = union
 	}
 	return ret, nil
 }
diff --git a/cdc/sink/codec/avro_test.go b/cdc/sink/codec/avro_test.go
index 5e5112553ae..159e3273b04 100644
--- a/cdc/sink/codec/avro_test.go
+++ b/cdc/sink/codec/avro_test.go
@@ -15,6 +15,7 @@ package codec
 
 import (
 	"context"
+	"encoding/json"
 	"time"
 
 	"github.com/linkedin/goavro/v2"
@@ -157,6 +158,80 @@ func (s *avroBatchEncoderSuite) TestAvroEncodeOnly(c *check.C) {
 	log.Info("TestAvroEncodeOnly", zap.ByteString("result", txt))
 }
 
+func (s *avroBatchEncoderSuite) TestAvroNull(c *check.C) {
+	defer testleak.AfterTest(c)()
+
+	table := model.TableName{
+		Schema: "testdb",
+		Table:  "TestAvroNull",
+	}
+
+	cols := []*model.Column{
+		{Name: "id", Value: int64(1), Flag: model.HandleKeyFlag, Type: mysql.TypeLong},
+		{Name: "colNullable", Value: nil, Flag: model.NullableFlag, Type: mysql.TypeLong},
+		{Name: "colNotnull", Value: int64(0), Type: mysql.TypeLong},
+		{Name: "colNullable1", Value: int64(0), Flag: model.NullableFlag, Type: mysql.TypeLong},
+	}
+
+	colInfos := []rowcodec.ColInfo{
+		{ID: 1, IsPKHandle: true, VirtualGenCol: false, Ft: types.NewFieldType(mysql.TypeLong)},
+		{ID: 2, IsPKHandle: false, VirtualGenCol: false, Ft: types.NewFieldType(mysql.TypeLong)},
+		{
+			ID: 3, IsPKHandle: false, VirtualGenCol: false,
+			Ft: setFlag(types.NewFieldType(mysql.TypeLong), uint(model.NullableFlag)),
+		},
+		{ID: 4, IsPKHandle: false, VirtualGenCol: false, Ft: types.NewFieldType(mysql.TypeLong)},
+	}
+
+	schema, err := ColumnInfoToAvroSchema(table.Table, cols)
+	c.Assert(err, check.IsNil)
+	var schemaObj avroSchemaTop
+	err = json.Unmarshal([]byte(schema), &schemaObj)
+	c.Assert(err, check.IsNil)
+	for _, v := range schemaObj.Fields {
+		if v["name"] == "colNullable" {
+			c.Assert(v["type"], check.DeepEquals, []interface{}{"null", "int"})
+		}
+		if v["name"] == "colNotnull" {
+			c.Assert(v["type"], check.Equals, "int")
+		}
+	}
+
+	native, err := rowToAvroNativeData(cols, colInfos, time.Local)
+	c.Assert(err, check.IsNil)
+	for k, v := range native.(map[string]interface{}) {
+		if k == "colNullable" {
+			c.Check(v, check.IsNil)
+		}
+		if k == "colNotnull" {
+			c.Assert(v, check.Equals, int64(0))
+		}
+		if k == "colNullable1" {
+			c.Assert(v, check.DeepEquals, map[string]interface{}{"int": int64(0)})
+		}
+	}
+
+	avroCodec, err := goavro.NewCodec(schema)
+	c.Assert(err, check.IsNil)
+	r, err := avroEncode(&table, s.encoder.valueSchemaManager, 1, cols, colInfos, time.Local)
+	c.Assert(err, check.IsNil)
+
+	native, _, err = avroCodec.NativeFromBinary(r.data)
+	c.Check(err, check.IsNil)
+	c.Check(native, check.NotNil)
+	for k, v := range native.(map[string]interface{}) {
+		if k == "colNullable" {
+			c.Check(v, check.IsNil)
+		}
+		if k == "colNotnull" {
+			c.Assert(v.(int32), check.Equals, int32(0))
+		}
+		if k == "colNullable1" {
+			c.Assert(v, check.DeepEquals, map[string]interface{}{"int": int32(0)})
+		}
+	}
+}
+
 func (s *avroBatchEncoderSuite) TestAvroTimeZone(c *check.C) {
 	defer testleak.AfterTest(c)()
 
@@ -198,7 +273,7 @@ func (s *avroBatchEncoderSuite) TestAvroTimeZone(c *check.C) {
 	res, _, err := avroCodec.NativeFromBinary(r.data)
 	c.Check(err, check.IsNil)
 	c.Check(res, check.NotNil)
-	actual := (res.(map[string]interface{}))["ts"].(map[string]interface{})["long.timestamp-millis"].(time.Time)
+	actual := (res.(map[string]interface{}))["ts"].(time.Time)
 	c.Check(actual.Local().Sub(timestamp), check.LessEqual, time.Millisecond)
 }