两者均可后接动名词(不接不定式)，区别如下：　　
1. 表示反复发生的动作(即动作之间略有间隔)时，两者可互换。如：　　
They kept (on) talking about it. 他们一直在谈论此事。　　
My shoe laces keep (on) coming undone. 我的鞋带老是松开。　　
2. 表示持续的状态或连续不断的动作(动作之间没有间隔)时, 通常只用 keep doing sth。如：　　
He kept standing during the meeting. 开会时他一直站着。　　
We kept hoping that they would have a chance to come to China some day. 我们一直希望他们什么时候有机会到中国来。　　
3. 表示将一直在做的事继续做下去，通常只用 keep on doing。如：　　
He kept on working after dark. 天黑了他还继续干。　　
Don’t give up; keep on trying. 别灰心，继续努力。　　
注：这样的 keep on doing可与 go on doing 换用。如：　　
The boys kept [went] on doing their homework in spite of interruptions. 尽管有干扰，孩子们仍继续做自己的作业。　　
4. 有时若意义明确，keep on 后的 doing sth 可省略，而 keep 后却不能省略 doing sth。如：　　
The rain kept on for several days. 雨一连下了好几天。　　


　　
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