两个或两个以上相继发生的动作，用and或but按动作发生的先后顺序连接，此时要用一般过去时，而不用过去完成时。过去完成时则强调主语在过去某一时刻回顾更早的动作。具体来说，当我们在谈论过去某一事件时，想到了在这之前已发生的某事，这时可以用过去完成时态。
例句
a. He opened the door and entered, but found nobody.
b. He served in the army for ten years, then retired and married. His children are now at school .
他当过十年兵，然后退伍并结了婚。他的孩子都在上学。
c. He had served in the airforce for ten years before he died in the jet-crash incident.
他在一次撞机事故中牺牲了，事故之前他已在空军服役了十年。
d. I realized that we had met before. （不能说…we met before）
e. I heard voices and realized that there were several people in the next room.
我听见有人说话，知道隔壁房间里有几个人。
f.I saw empty glasses and cigar butts on the table and realized that someone had been in the room.
我看见桌上有空杯子和雪茄烟蒂，知道屋子里有人来过。
在表示两个相继发生的动作时，用过去完成时可以表示在一个动作完成以后，另一个动作才开始发生，从而使得两个动作相互独立，彼此脱离开来。用一般过去时，则可能表示一个动作的发生“导致”另一个动作的发生，或两个动作之间有因果关系。
试比较：
a. When I had opened all the windows I sat down and had a cup of tea.
我把所有的窗子都打开后，就坐下来喝了杯茶。（不宜说When I opened…）
b. I opened the window and the cat jumped out.
我刚把窗子打开，那只猫就跳了出去。
c. When I had written my letters I did some gardening.
我把信写完后，到花园里干了些活。（不宜说When I wrote…）
d. When I wrote him a letter, he came at once.
我给他去了封信后，他立即就来了。
e. When the singer had sung her song, she sat down.
这位歌手唱完歌以后，就坐了下来。（若说成When the singer sangher song, she sat down.则可能给人造成这种印象：这位歌手是坐着唱歌的。）