用表示时间的连词连接一个句子作状语，这样的主从复合句就是时间状语从句。连接时间状语从句的连接词有：when, before, after, while, as soon as, until, since...... 这里要注意一点的是，如果主句是一般将来时，从句只能用一般现在时表示将来意义。引导时间状语从句的连词主要有三类：
一、普通连词：如after, as, before, since, till, until, when, while等。
例如：
1.I will tell you after they leave.他们走我再告诉你。
2.I'd better have a think before I decide. 我最好还是先想想再作决定。
3.He waited until she was about to leave. 他等着一直到她准备离开。
4.Stand still while I take your photograph. 我给你拍照时站着不要动。
二、表示“一……就......”的连词：如：as soon as，the moment, the minute, the second, the instant, immediately, directly, instantly, once, no sooner…than, hardly…when等。
例如：
1.The moment I saw him I knew there was no hope. 我一看到他就知道没希望了。
2.I want to see him the minute (that) he arrives. 他一来到我就要见他。
3.The instant he opened the door he saw the thief. 他一开门就看见了这个贼。
4.Once he arrives, we can start. 他一来我们就可以开始。
5.We had no sooner set out than it began to rain. 我们刚出发就下雨了。
三、含有time的连词：这类连词主要有every time(每次)，each time(每次)，(the) next time(下次)，any time(随时)，(the) last time(上次)，the first time(第一次), by the time(当……的时候)。例如：
1.You can call me any time you want to. 你随时都可以给我打电话。
2.Each time I went there, I saw him working. 我每次去那儿都看见他在工作。
3.Next time you come in, please close the door. 下次你进来，请关门。
4.He didn't tell me the last time I saw him. 我上次见到他时他没告诉我。
注意：every time, each time, any time前不用冠词，(the) next time, (the) last time中的冠词可以省略，而the first time中的冠词通常不能省略。