1. could have done表示过去本来有做某事的打算、机会或意图，但实际上没有实现；即过去的事情有可能发生，但说话者确切知道并未发生，通常译为“本来可以”。
I could have lent you the money. Why didn’t you ask me? 我本来可以借这笔钱给你的。你为什么不向我提出?
I could have passed my examination easily but I made too many stupid mistakes. 我本可以轻易通过考试，但我犯了太多不该犯的错误。
The accident could have been avoided.
这个事故本来是可以避免的。
I could have done without being woken up at three in the morning.
其实用不着在凌晨三点钟就把我叫醒。
The accident could have been much worse; luckily no harm was done.
这次事故本来可能糟糕得多；所幸没有造成伤害。
The accident could have been prevented.
这次事故本来是可以防止的。
I could have wept thinking about what I'd missed.
想到所失去的东西，我真想痛哭一场。
I could have won the game but decided to let her win.
我本可以赢得那场比赛，但还是决定让她赢了。
She could have been a brilliant pianist if she'd put her mind to it.
如果她专心致志，坚持到底，她本可以成为一名杰出的钢琴家。
We could have given you a ride this morning, but the car was full.
今天早上我们本可以载你一程的，但车已经满了。
Some women could have made a good salary in a job instead of staying house, but they decided not to work for the sake of the family.（四级真题）
一些女性本可以在工作中获得高薪，而不是呆在家里，但为了家庭，她们决定不工作。
2. could have done表推测、估计某事过去有可能发生，至于该事是否真的发生不确切知道。
此时和might have done可以互换。
The letter could have got lost in the post.
这封信可能是在邮递中丢失了。
You easily could have left your hotel room unseen.《达芬奇密码》
你可能在别人看不到的情况下轻易地离开了酒店。
He learned to speak the language so quickly and well that he could have been taken for a native speaker.
他学得如此之快，如此之好，以至于他可能被认为是一个以英语为母语的人。
It's not funny! Someone could have been hurt.
这没什么好玩的！可能有人会受到伤害。
If I had followed your advice, I could/might have been promoted.
如果那时我听了你的建议，我可能就升职了。
When Della revived, she complained that I had scared her and that she could have gotten hurt when she fell over.
当德拉苏醒过来时，她抱怨说我吓坏了她，还抱怨说她晕倒时可能受了伤。
《亲历历史》希拉里
If I hadn’t worked hard, I could/might have failed the exam.
如果我没有好好学习，我可能就挂科了。（could have done表对过去肯定的推测估计时常常译为：可能会/可能就）
She could not have been on that flight because I just saw her at work.
她那时不可能在飞机上，因为我刚才看见她在上班呢。（could not have done表示对过去否定的推测估计常常译为：在那个时候、当时、那时不可能）
My mother and my grandmothers could never have lived my life; my father and my grandfathers could never have imagined it.
我的母亲、祖母和外祖母在当时是不可能经历过我的生活；我的父亲、祖父和外祖父在当时不可能想象出我的生活。《亲历历史》希拉里
You couldn't have left it on the bus, could you?
你不可能把它落在公共汽车上了吧？
It couldn't have been me ─ it must have been someone else.
那不可能是我——准是别人。
《牛津高阶英汉双解词典》
The extent of the damage could not have been foreseen.
损害的程度是无法预见到的。
Police believe his wife could not have administered the poison.
警方认为他的妻子是不可能下毒的。
He could not possibly have been poisoned as popular legend has it.
他不可能像民间传说的那样被下了毒。
She could not have taken these massive doses orally. In the first place, she did not have enough pills.
她不可能口服这么大的剂量，因为她根本没有足够的药丸了。
He could not have seen me yesterday, because I wasn't there.
昨天他不可能见到我，因为当时我不在那里。
The damage couldn't have been caused accidentally.
这次损毁不可能是偶然因素造成的。
He couldn't have been more than fourteen years old.
他不可能超过14岁。
At the time we couldn't have anticipated the result of our campaigning
那时我们不可能预料到我们这项运动的结果。
He could never have foreseen that one day his books would sell in millions.
他从来没预想过有一天他的书会卖掉几百万本。
So how you get into the castle?
I hid in a farmer’s cart which was taking vegetable into the castle.
The guards couldn’t have been watching very carefully.
那你是怎么进入城堡的？
我藏在农民送蔬菜的马车里进入城堡的。
那些卫兵们不可能总是察看得那么仔细。（couldn’t have been doing不可能总是）
…her father could not have made such a mistake.(新概念3，L60)）
她父亲（那时）不可能犯那样的错误。
I couldn’t have got to the meeting on time—unless I had caught an earlier train.
我那时是绝不可能准是到达会场的，除非我赶上了较早一班火车。
Mary couldn’t have received my letter, otherwise she would have replied before now.
玛丽那时不可能收到我的信，否则她早就回信了。（研考真题）
There were already five people in the car but they managed to take me as well.
It couldn’t have been a comfortable journey.
车上那时已经有五个人了，但他们也设法把我带走了。
那不可能是一次舒适的旅行。（高考真题）
He couldn’t have caught the 8:20 bus because he didn’t leave home till 8:25.
他那时不可能赶上了八点二十分的公共汽车，因为他八点二十五分才出门的。（专四真题）
We could not have provided him with a detached house when he came, but he had specifically asked for a small flat.
他来的时候，我们不可能给他提供一套独立的房子，但之前他特别要求过需要一套小公寓。专四真题）
最后试比较：could/might have done和would have done用法含义不同之处
If I had known that you needed help, I could/might have helped you.（无语境可以有两种翻译）
（1）如果我知道你那时候需要帮助，我本来可以去帮助你。
（2）如果我知道你那时候需要帮助，我可能去帮助你。
（表示本来可以有机会、可能做的事，但是事实没有做；也可以表示对过去的事情的推测和估计，不强调有没有做）
If I had known that you needed help, I would have helped you.
如果我知道你那时候需要帮助，我本来会去帮助你。（表示主观愿意去做，但是由于种种原因没做成）