Would与used to都可用来表示过去经常性或习惯性的动作,常常可以换用。如:
(1)When we were boys we used to/would go swimming every summer.
(2)He used to/would spend every penny he earned on books.
Would与used to都不能用来表示动作发生的具体频度或具体的一段时间。例如,不能说:
(3) I would/used to go to France six times.
(4)He used to live in Africa for twenty years.
(5)I went to France six times. 我去过法国6次。
(6)He lived in Africa for twenty years. 他在非洲住过20年。
Would与used to的区别主要有以下几点:
a. Used to可指过去的状态或情况,would则不能。如:
(7)School children used to know the story of how Abraham Lincoln walked five miles to return a penny he'd
overcharged a customer.(不能用would)
(8)Yet,he cannot but remember China as it used to be.然而,他不会不记得旧日的中国(不能用would)。
b. Would表示反复发生的动作。如果某一动作没有反复性,就不能用 would,只能用 used to。例如:
(9) And from that day on, as soon as the table was cleared and the dishes were gone. Mother would disappear
into her sewing room to practice.
(10)I used to live in Beijing. 我过去住在北京。(没有反复性)
c. Used to表示过去经常性或习惯性的动作或状态现在已经结束,would则表示有可能再发生。如:
(11)People used to believe that the earth was flat.
(12)He would go to the park as soon as he was free.
注意:used to的否定式和疑问句:
I used not to like opera.
I usedn't to like opera.
I didn't use to like opera.
used you to like opera?
Did you use to like opera?
(15)Didn't you use to like opera? 你过去不喜欢歌剧吗?
(16)You used to like opera, didn't you? 你过去喜欢歌剧,是吗?
(17)There used to be a church here, usedn't there? 过去这里有座教堂,是不是?
怎样分辨would与used to用法上的异同: http://insuns.com/article/16335-1.html