没有多大区别 。an then在用法上比then要严格，不能直接用在名词后，要不就整体放在名词前，要不就拆开在名词前后。
Then：副词，意味着在那个时候，在这种情况下，下一个，或也——“He laughed and thenhe cried.”
I answered two questions and then got stuck.（我回答了两个问题，然后就不懂了。）
I sit up, and through the venetian blinds I can see the palm trees shaking wildly, actually bending, in the hot winds, and then I stare back at the poster and then turn away and then look back again at the smile and the mocking eyes.
（我坐起来，通过百叶窗可以看到棕榈树在热风中摇晃，树干已经弯曲，然后我看了看海报就转身走开，之后又回头看着那双嘲笑的眼睛。）
扩展资料
1、He teed the ball up carefully and then teed off.
他把球小心地放在球座上，然后开球。
2、He sucked at his cigar and then agreed with what I said.
他吸了一口雪茄，然后对我所说的表示同意。
3、I heaved him up and then put him down on the ground lightly.
我奋力把他举了起来，然后又把他轻轻地放到了地上。
4、I'll show you how to hit the ball and then you must copy [follow] my example.
我先做给你看如何击球，然后你必须照我的示范去做。