should + have + 过去分词

1. 表示主观推测

指对可能已经发生的情况作主观猜测，其意为“大概已经”“应该已经”。如：

The letter should have arrived by now. 信现在该到了。
I can't think why he should have been so angry. 我想不通他怎么会这样生气。

注：该用法中的should也可换成ought to，意思不变。如：

The train should [ought to] have already left. 火车大概已经开走了吧。

2. 表示责备或批评

表示过去本来应该发生而实际上没有发生的情况，往往含有遗憾、责备、批评等感情色彩，通常可译为“应该”“本来应该”等。如：

You should have reported the matter to the police. 你本应该把这件事报告警察。
I beg your pardon. I suppose I should have knocked. 对不起，我想我应该先敲一下门的。

如果是否定式，则表示本来不该发生的情况却发生了。如：

You shouldn't have opened her letter. 你是不应该拆她的信的。
She shouldn't have stood in a queue. She should have got tickets from the machine. 她本来就不该去排队，她应该在售票机那儿买票。

注：该用法中的should也可换成ought to，意思不变。如：

You should [ought to] have told us earlier. 你应该早点告诉我们的。
You shouldn't [oughtn't to] have parked there. 你本不该把车停在这里。

3. 表示惊讶

表示对已经发生的情况表示惊讶或不理解，通常含有“竟然”的意味。如：

It is a pity that he should have failed in the exam. 他考试竟然没有及格，真是可惜。
I can't think why he should have said that it was my fault. 我真不明白，他怎么竟然说这是我的过错。

4. 用于虚拟语气

在虚拟条件句中，当谈论过去的情况时，其句型通常是：主句用“could / would / should /might +have+过去分词”，从句用过去完成时。如：

If I had seen her I should have invited her. 我当时要是看到她的话我本会邀请她的。
If he had received the present, he should have thanked her. 如果他收到了礼物，他是应当向她道谢的。
I should not have laughed if I had thought you were serious. 如果我想到你是认真的，我就不会笑了。