used to do和be used to doing的含义不同，be used to doing表达惯于做某事的意思；used to所表示的意思是“过去常常做某事”，强调过去发生的事，所以一般用于描述发生在过去的事情。

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

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

疑问形式是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.

我惯于早上喝一杯茶。