diff --git a/ddl/ddl.go b/ddl/ddl.go
index dd33031182..f99cd7f424 100644
--- a/ddl/ddl.go
+++ b/ddl/ddl.go
@@ -1206,10 +1206,6 @@ func getAnonymousIndex(t table.Table, colName model.CIStr) model.CIStr {
 }
 
 func (d *ddl) CreateIndex(ctx context.Context, ti ast.Ident, unique bool, indexName model.CIStr, idxColNames []*ast.IndexColName) error {
-	err := checkDuplicateColumnName(idxColNames)
-	if err != nil {
-		return errors.Trace(err)
-	}
 	is := d.infoHandle.Get()
 	schema, ok := is.SchemaByName(ti.Schema)
 	if !ok {
@@ -1433,20 +1429,6 @@ func findCol(cols []*model.ColumnInfo, name string) *model.ColumnInfo {
 	return nil
 }
 
-// checkDuplicateColumnName checks if index exists duplicated columns.
-func checkDuplicateColumnName(indexColNames []*ast.IndexColName) error {
-	for i := 0; i < len(indexColNames); i++ {
-		name1 := indexColNames[i].Column.Name
-		for j := i + 1; j < len(indexColNames); j++ {
-			name2 := indexColNames[j].Column.Name
-			if name1.L == name2.L {
-				return infoschema.ErrColumnExists.GenByArgs(name2)
-			}
-		}
-	}
-	return nil
-}
-
 // DDL error codes.
 const (
 	codeInvalidWorker         terror.ErrCode = 1
diff --git a/plan/validator.go b/plan/validator.go
index 2113861809..1804225851 100644
--- a/plan/validator.go
+++ b/plan/validator.go
@@ -42,7 +42,7 @@ type validator struct {
 }
 
 func (v *validator) Enter(in ast.Node) (out ast.Node, skipChildren bool) {
-	switch in.(type) {
+	switch node := in.(type) {
 	case *ast.AggregateFuncExpr:
 		if v.inAggregate {
 			// Aggregate function can not contain aggregate function.
@@ -51,12 +51,17 @@ func (v *validator) Enter(in ast.Node) (out ast.Node, skipChildren bool) {
 		}
 		v.inAggregate = true
 	case *ast.CreateTableStmt:
-		v.checkCreateTableGrammar(in.(*ast.CreateTableStmt))
+		v.checkCreateTableGrammar(node)
 		if v.err != nil {
 			return in, true
 		}
 	case *ast.CreateIndexStmt:
-		v.checkCreateIndexGrammar(in.(*ast.CreateIndexStmt))
+		v.checkCreateIndexGrammar(node)
+		if v.err != nil {
+			return in, true
+		}
+	case *ast.AlterTableStmt:
+		v.checkAlterTableGrammar(node)
 		if v.err != nil {
 			return in, true
 		}
@@ -196,6 +201,17 @@ func (v *validator) checkCreateTableGrammar(stmt *ast.CreateTableStmt) {
 			return
 		}
 	}
+	for _, constraint := range stmt.Constraints {
+		switch tp := constraint.Tp; tp {
+		case ast.ConstraintKey:
+			err := checkDuplicateColumnName(constraint.Keys)
+			if err != nil {
+				v.err = err
+				return
+			}
+		}
+	}
+
 }
 
 func isPrimary(ops []*ast.ColumnOption) int {
@@ -208,14 +224,41 @@ func isPrimary(ops []*ast.ColumnOption) int {
 }
 
 func (v *validator) checkCreateIndexGrammar(stmt *ast.CreateIndexStmt) {
-	for i := 0; i < len(stmt.IndexColNames); i++ {
-		name1 := stmt.IndexColNames[i].Column.Name
-		for j := i + 1; j < len(stmt.IndexColNames); j++ {
-			name2 := stmt.IndexColNames[j].Column.Name
-			if name1.L == name2.L {
-				v.err = infoschema.ErrColumnExists.GenByArgs(name2)
-				return
+	v.err = checkDuplicateColumnName(stmt.IndexColNames)
+	return
+}
+
+func (v *validator) checkAlterTableGrammar(stmt *ast.AlterTableStmt) {
+	specs := stmt.Specs
+	for _, spec := range specs {
+		switch spec.Tp {
+		case ast.AlterTableAddConstraint:
+			switch spec.Constraint.Tp {
+			case ast.ConstraintKey, ast.ConstraintIndex, ast.ConstraintUniq, ast.ConstraintUniqIndex,
+				ast.ConstraintUniqKey:
+				v.err = checkDuplicateColumnName(spec.Constraint.Keys)
+				if v.err != nil {
+					return
+				}
+			default:
+				// Nothing to do now.
 			}
+		default:
+			// Nothing to do now.
 		}
 	}
 }
+
+// checkDuplicateColumnName checks if index exists duplicated columns.
+func checkDuplicateColumnName(indexColNames []*ast.IndexColName) error {
+	for i := 0; i < len(indexColNames); i++ {
+		name1 := indexColNames[i].Column.Name
+		for j := i + 1; j < len(indexColNames); j++ {
+			name2 := indexColNames[j].Column.Name
+			if name1.L == name2.L {
+				return infoschema.ErrColumnExists.GenByArgs(name2)
+			}
+		}
+	}
+	return nil
+}
diff --git a/plan/validator_test.go b/plan/validator_test.go
index 2e419c4b22..675c61841d 100644
--- a/plan/validator_test.go
+++ b/plan/validator_test.go
@@ -54,7 +54,9 @@ func (s *testValidatorSuite) TestValidator(c *C) {
 		{"create table t(id int auto_increment) ENGINE=MYISAM", true, nil},
 		{"create table t(a int primary key, b int, c varchar(10), d char(256));", true, errors.New("Column length too big for column 'd' (max = 255); use BLOB or TEXT instead")},
 		{"create index ib on t(b,a,b);", true, errors.New("[schema:1060]Duplicate column name 'b'")},
+		{"create table t (a int, b int, key(a, b, A))", true, errors.New("[schema:1060]Duplicate column name 'A'")},
 		{"create table t(c1 int not null primary key, c2 int not null primary key)", true, errors.New("Multiple primary key defined")},
+		{"alter table t add index idx(a, b, A)", true, errors.New("[schema:1060]Duplicate column name 'A'")},
 	}
 	store, err := tidb.NewStore(tidb.EngineGoLevelDBMemory)
 	c.Assert(err, IsNil)