diff --git a/internal/parser/planparserv2/parser_visitor.go b/internal/parser/planparserv2/parser_visitor.go
index 5147144dd3d..14fee3a3170 100644
--- a/internal/parser/planparserv2/parser_visitor.go
+++ b/internal/parser/planparserv2/parser_visitor.go
@@ -826,7 +826,7 @@ func (v *ParserVisitor) getColumnInfoFromStructSubField(tokenText string) (*plan
 	}
 
 	// Construct full field name for struct array field
-	fullFieldName := v.currentStructArrayField + "[" + fieldName + "]"
+	fullFieldName := typeutil.ConcatStructFieldName(v.currentStructArrayField, fieldName)
 	// Get the struct array field info
 	field, err := v.schema.GetFieldFromName(fullFieldName)
 	if err != nil {
@@ -2202,7 +2202,7 @@ func (v *ParserVisitor) VisitStructSubField(ctx *parser.StructSubFieldContext) i
 	}
 
 	// Construct full field name for struct array field
-	fullFieldName := v.currentStructArrayField + "[" + fieldName + "]"
+	fullFieldName := typeutil.ConcatStructFieldName(v.currentStructArrayField, fieldName)
 	// Get the struct array field info
 	field, err := v.schema.GetFieldFromName(fullFieldName)
 	if err != nil {
diff --git a/internal/util/indexparamcheck/stl_sort_checker.go b/internal/util/indexparamcheck/stl_sort_checker.go
index 908d227ba84..f9735c27ee8 100644
--- a/internal/util/indexparamcheck/stl_sort_checker.go
+++ b/internal/util/indexparamcheck/stl_sort_checker.go
@@ -20,6 +20,13 @@ func (c *STLSORTChecker) CheckTrain(dataType schemapb.DataType, elementType sche
 
 func (c *STLSORTChecker) CheckValidDataType(indexType IndexType, field *schemapb.FieldSchema) error {
 	dataType := field.GetDataType()
+	if typeutil.IsArrayType(dataType) && typeutil.IsStructSubField(field.GetName()) {
+		elemType := field.GetElementType()
+		if !typeutil.IsArithmetic(elemType) && !typeutil.IsStringType(elemType) && !typeutil.IsTimestamptzType(elemType) {
+			return errors.New(fmt.Sprintf("STL_SORT are only supported on numeric, varchar or timestamptz field, got struct sub-field of %s", field.GetElementType()))
+		}
+		return nil
+	}
 	if !typeutil.IsArithmetic(dataType) && !typeutil.IsStringType(dataType) && !typeutil.IsTimestamptzType(dataType) {
 		return errors.New(fmt.Sprintf("STL_SORT are only supported on numeric, varchar or timestamptz field, got %s", field.GetDataType()))
 	}
diff --git a/internal/util/indexparamcheck/stl_sort_checker_test.go b/internal/util/indexparamcheck/stl_sort_checker_test.go
index 007adaff08e..a71b0c650db 100644
--- a/internal/util/indexparamcheck/stl_sort_checker_test.go
+++ b/internal/util/indexparamcheck/stl_sort_checker_test.go
@@ -19,4 +19,14 @@ func Test_STLSORTIndexChecker(t *testing.T) {
 
 	assert.Error(t, c.CheckValidDataType(IndexSTLSORT, &schemapb.FieldSchema{DataType: schemapb.DataType_Bool}))
 	assert.Error(t, c.CheckValidDataType(IndexSTLSORT, &schemapb.FieldSchema{DataType: schemapb.DataType_JSON}))
+
+	// struct sub-fields: name follows "structName[fieldName]" convention, DataType is Array
+	assert.NoError(t, c.CheckValidDataType(IndexSTLSORT, &schemapb.FieldSchema{Name: "myStruct[age]", DataType: schemapb.DataType_Array, ElementType: schemapb.DataType_Int64}))
+	assert.NoError(t, c.CheckValidDataType(IndexSTLSORT, &schemapb.FieldSchema{Name: "myStruct[score]", DataType: schemapb.DataType_Array, ElementType: schemapb.DataType_Float}))
+	assert.NoError(t, c.CheckValidDataType(IndexSTLSORT, &schemapb.FieldSchema{Name: "myStruct[name]", DataType: schemapb.DataType_Array, ElementType: schemapb.DataType_VarChar}))
+	assert.Error(t, c.CheckValidDataType(IndexSTLSORT, &schemapb.FieldSchema{Name: "myStruct[flag]", DataType: schemapb.DataType_Array, ElementType: schemapb.DataType_Bool}))
+	assert.Error(t, c.CheckValidDataType(IndexSTLSORT, &schemapb.FieldSchema{Name: "myStruct[meta]", DataType: schemapb.DataType_Array, ElementType: schemapb.DataType_JSON}))
+
+	// regular Array field (not a struct sub-field) should still be rejected
+	assert.Error(t, c.CheckValidDataType(IndexSTLSORT, &schemapb.FieldSchema{Name: "tags", DataType: schemapb.DataType_Array, ElementType: schemapb.DataType_Int64}))
 }
diff --git a/pkg/util/typeutil/schema.go b/pkg/util/typeutil/schema.go
index 29c40d6b5d8..c9e1d793064 100644
--- a/pkg/util/typeutil/schema.go
+++ b/pkg/util/typeutil/schema.go
@@ -2667,6 +2667,12 @@ func ConcatStructFieldName(structName string, fieldName string) string {
 	return fmt.Sprintf("%s[%s]", structName, fieldName)
 }
 
+// IsStructSubField checks if a field name follows the "structName[fieldName]" convention,
+// indicating it is a sub-field within a StructArrayField.
+func IsStructSubField(fieldName string) bool {
+	return strings.Contains(fieldName, "[")
+}
+
 func ExtractStructFieldName(fieldName string) (string, error) {
 	parts := strings.Split(fieldName, "[")
 	if len(parts) == 1 {