diff --git a/expression/expr_to_pb_test.go b/expression/expr_to_pb_test.go
index 4baf924a1b4ff..7a6459fb1a091 100644
--- a/expression/expr_to_pb_test.go
+++ b/expression/expr_to_pb_test.go
@@ -522,6 +522,7 @@ func TestExprPushDownToFlash(t *testing.T) {
 	int32Column := genColumn(mysql.TypeLong, 8)
 	float32Column := genColumn(mysql.TypeFloat, 9)
 	enumColumn := genColumn(mysql.TypeEnum, 10)
+	durationColumn := genColumn(mysql.TypeDuration, 11)
 
 	function, err := NewFunction(mock.NewContext(), ast.JSONLength, types.NewFieldType(mysql.TypeLonglong), jsonColumn)
 	require.NoError(t, err)
@@ -1125,6 +1126,11 @@ func TestExprPushDownToFlash(t *testing.T) {
 	require.NoError(t, err)
 	exprs = append(exprs, function)
 
+	// TimeToSec
+	function, err = NewFunction(mock.NewContext(), ast.TimeToSec, types.NewFieldType(mysql.TypeDuration), durationColumn)
+	require.NoError(t, err)
+	exprs = append(exprs, function)
+
 	pushed, remained = PushDownExprs(sc, exprs, client, kv.TiFlash)
 	require.Len(t, pushed, len(exprs))
 	require.Len(t, remained, 0)
diff --git a/expression/expression.go b/expression/expression.go
index 9965ce0a7cecc..0709acae46a57 100644
--- a/expression/expression.go
+++ b/expression/expression.go
@@ -1059,7 +1059,8 @@ func scalarExprSupportedByFlash(function *ScalarFunction) bool {
 		ast.InetNtoa, ast.InetAton, ast.Inet6Ntoa, ast.Inet6Aton,
 		ast.Coalesce, ast.ASCII, ast.Length, ast.Trim, ast.Position, ast.Format,
 		ast.LTrim, ast.RTrim, ast.Lpad, ast.Rpad, ast.Regexp,
-		ast.Hour, ast.Minute, ast.Second, ast.MicroSecond:
+		ast.Hour, ast.Minute, ast.Second, ast.MicroSecond,
+		ast.TimeToSec:
 		switch function.Function.PbCode() {
 		case tipb.ScalarFuncSig_InDuration,
 			tipb.ScalarFuncSig_CoalesceDuration,
diff --git a/planner/core/integration_test.go b/planner/core/integration_test.go
index 63e9d118507a3..a55acf9f5d89f 100644
--- a/planner/core/integration_test.go
+++ b/planner/core/integration_test.go
@@ -2726,6 +2726,41 @@ func TestIssue18984(t *testing.T) {
 		"3 3 3 2 4 3 5"))
 }
 
+func TestTimeToSecPushDownToTiFlash(t *testing.T) {
+	store, clean := testkit.CreateMockStore(t)
+	defer clean()
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t")
+	tk.MustExec("create table t(a time(4))")
+	tk.MustExec("insert into t values('700:10:10.123456')")
+	tk.MustExec("insert into t values('20:20:20')")
+	tk.MustExec("set @@tidb_allow_mpp=1; set @@tidb_enforce_mpp=1")
+	tk.MustExec("set @@tidb_isolation_read_engines = 'tiflash'")
+
+	// Create virtual tiflash replica info.
+	dom := domain.GetDomain(tk.Session())
+	is := dom.InfoSchema()
+	db, exists := is.SchemaByName(model.NewCIStr("test"))
+	require.True(t, exists)
+	for _, tblInfo := range db.Tables {
+		if tblInfo.Name.L == "t" {
+			tblInfo.TiFlashReplica = &model.TiFlashReplicaInfo{
+				Count:     1,
+				Available: true,
+			}
+		}
+	}
+
+	rows := [][]interface{}{
+		{"TableReader_9", "10000.00", "root", " data:ExchangeSender_8"},
+		{"└─ExchangeSender_8", "10000.00", "mpp[tiflash]", " ExchangeType: PassThrough"},
+		{"  └─Projection_4", "10000.00", "mpp[tiflash]", " time_to_sec(test.t.a)->Column#3"},
+		{"    └─TableFullScan_7", "10000.00", "mpp[tiflash]", "table:t", "keep order:false, stats:pseudo"},
+	}
+	tk.MustQuery("explain select time_to_sec(a) from t;").Check(rows)
+}
+
 func TestBitColumnPushDown(t *testing.T) {
 	store, clean := testkit.CreateMockStore(t)
 	defer clean()