used to do和be used to doing的含義不同，be used to doing表達慣于做某事的意思；used to所表示的意思是“過去常常做某事”，強調過去發(fā)生的事，所以一般用于描述發(fā)生在過去的事情。

used to do的否定形式是didn't use to do 或 usedn't to do；疑問形式是Did you use to do sth?

例句：My brother used to go swimming in the sea.我哥哥過去常常在海里游泳。否定形式是My brotherdidn't use to go swimming in the sea.

疑問形式是Did your brother use to go swimming in the sea?

be used to doing的例句：I am used to having a cup of tea in the morning.

我慣于早上喝一杯茶。