来自百度百科
英语中的被动句
谓语动词的语态表示句子的主语和谓语动作之间的关系
1）当句子的主语是谓语动作的执行者时，主、谓之间的关系称为主动语态；
2）当句子的主语是谓语动作的承受者时，主、谓之间的关系称为被动语态。例如：
I teach English.（主动语态）我教英语。
Our English is taught by him.（被动语态）我们的英语是由他教的。
He speaks English.（主动语态）他说英文。
English is spoken in many countries all over the world.（被动语态）世界许多国家都讲英语。
在被动语态的句子中，谓语部分的结构是be + p.p.（过去分词）。被动语态的句子有时态的变化，这个变化反映在be动词上。也就是说，把一个句子做成被动语态的句子，只需要写出BE动词的所需时态，再加上所给动词的过去分词就行了。当然，这只是指谓语部分而言。我们知道，be动词作为一个独立的谓语动词有自己现在分词（being）和过去分词 （been）。那么，下面我们来看看be在各种时态中的变化形式：
一般现在时 am / is / are
一般过去时 was / were
一般将来时 shall / will + be
过去将来时 would / should + be
现在进行时 am / is / are + being
过去进行时 was / were + being
现在完成时 have / has + been
过去完成时 had + been
说明：1）以上的八个时态可用于被动式，其它没有列举的时态都不宜用于被动语态的句子中。2）另外，表中被斜线隔开的词表示，供根据具体情况作选择。弄清楚了be在各种时态中的变化形式以后，我们就能很轻松地写出被动语态的各种时态了。我们可看看下面的实例：
English is spoken in many countries all over the world .（一般现在时）
世界上许多国家都讲英文。
Some TV sets for sale in the department store were stolen last night. （一般过去时）
那家商场用来出售的部分电视机昨晚被盗。
He won't be allowed, by his father, to marry lucy. （一般将来时）
他父亲不会让他娶露西为妻的。
They would be sent to the army when they finished the training. （过去将来时）
他们结束训练时将被派往部队。
The project is being carried out.（现在进行时）
这个计划正在执行中。
The case was being investigated then.（过去进行时）
那时这案子正在调查中。
This novel has been translated into several languages. （现在完成时）
这本小说已被译成了几种语言。
They said that production costs had been reduced. （过去完成时）
他们说生产成本已经下降了。
一般来说，在我们日常生活中，能用主动语态的时候就尽量不去用被动语态。
只有在下列情况中我们才用被动语态：
1）不清楚动作的执行者是谁, 例如:
The front window in the classroom was broken yesterday. 昨天，教室的前窗被打破了。
The time-table has been changed .时间表已变动了。
We haven't been informed of it .还没有人通知我们这事儿。
2)说话人对宾语的兴趣大于对主语的兴趣（这时可用by引导出动作的执行者），例如：
My TV set is being repaired in the shop. 我的电视机正在这店里修。
These books are written especially for children. 这些书是专门为孩子们写的。
The song was composed by a young worker. 这首歌是一位年青工人谱写的。
3) 不愿意说出动作的执行者，其目的是为了使语言得体、圆滑等。在这种情况下，有时常用一些句式，如"It is said that…"（据说……），"It is reported that …"（据报道……），"It is rumoured that …"（据传言……）等等。例如：
You are requested to make a speech at next meeting. 请您在下次会议上作个发言。
It is said that she is going to be married to a foreigner. 据说她要嫁给一个外国人。
It is rumored that he has been appointed as successor to the president of our company . 据传闻，他已被任命为我们公司总裁的接班人了。
It is generally considered impolite to ask one's age, salary, marriage, etc.. 问别人的年龄、工资、婚姻状况等通常被认为是不礼貌的。
4) 出于修辞的原因，或是说为了更好地安排句子。例如：
The professor came to our school and warmly welcomed by the teachers and students.（句子的后半句用被动式就可以只安排一个主语。）那位教授来到我校并受到师生们的热烈欢迎。
I went to the party and was asked by my friends to do some cooking for them. （同上）我去参加了那个聚会，朋友们还请我为他们烧了几样菜。
The notion is especially opposed to by those who have invested much in the area.
（此句若选those作主语，就会使主语与谓语相距太远而显得句子松散，因为它的定太长了。）这个提议特别遭到了那些在本地区投资很大的人的反对。
这里我们还要进一步谈谈几种特殊的被动结构。
1）关于带情态动词的被动结构
带情态动词的被动结构的固定句式为"情态动词 + be + 过去分词"。也有个别带"to"的情态动词例外，如：ought to和have to ，它们的被动结构就只能在不定式中。例如：
The debt must be paid off before next month. 那笔债务必须在下个月前付清。
The debt has to be paid off before next month. 那笔债务必须在下个月前付清。
Oil can be turned into energy by burning it. 油经过燃烧可变为能原。
You ought to be criticized for your carelessness. 你由于粗心大意应当受到批评。
2) 关于带有两个宾语的主动态变成被动态
我们先来看看"带有两个宾语的主动态句子的结构"，重点看谓语部分 ：
She sent me a novel on my birthday .
主 谓 间接宾语 直接宾语 状语
I allowed him an hour to finish the work .
主 谓 间接宾语 直接宾语 状语
从上面的分析可以看出，两个宾语分别是：直接宾语和间接宾语。将这种主动态的句子变成被动态的句子，可选两个宾语中的任何一个作为被动态句子的主语，而将另一个宾语作为"保留宾语"写入被动态的句中。但有一点要说明，那就是，如果你选直接宾语作"主语"，有时要在被动态句子的"保留宾语"前加上合适的介词。因为这些动词常有两种句式，即：我们可以说give sb sth , send sb sth , buy sb sth ；我们也可以说give sth to sb, send sth to sb , buy sth for sb 。请看下面两种情况的对照：
She sent me a novel on my birthday. (主动)
I was sent a novel on my birthday. (被动)
A novel was sent to me on my birthday. (被动)
My brother bought me a watch yesterday. (主动)
I was bought a watch yesterday. (被动)
A watch was bought for me by my brother yesterday.(被动)
3)关于带有复合宾语的主动态变成被动态
如果将带有复合宾语（既：宾语 + 宾语补足语）的主动态的句子变成被动态的句子，我们只能选择原来句子的宾语作被动态句子的主语；而这时，原句里的宾语补足语现在就变成被动态句子的"主语补足语"了。例如：
The story made us laugh .(宾语补足语)
We were made to laugh by the story. (主语补足语)
They asked me to help them. (宾语补足语)
I was asked to help them. (主语补足语)
We saw them coming over. (宾语补足语)
They were seen coming over. (主语补足语)
一、 被动语态的用法：
1. 一般现在时的被动语态构成：is / am / are + 及物动词的过去分词
Our classroom is cleaned everyday.
I am asked to study hard.
Knives are used for cutting things.
2. 一般过去时的被动语态构成：was / were + 及物动词的过去分词
A new shop was built last year.
Dinosaur eggs were laid long long ago.
3. 现在完成时的被动语态构成：has / have + been + 及物动词的过去分词
This book has been translated into many languages.
Many man-made satellites have been sent up into space by many countries.
4. 一般将来时的被动语态构成：will+ be + 及物动词的过去分词
A new hospital will be built in our city.
Many more trees will be planted next year.
5. 含有情态动词的被动语态构成：情态动词+ be + 及物动词的过去分词
Young trees must be watered often.
Your mistakes should be corrected right now.
The door may be locked inside.
Your homework can be handed in tomorrow.
6. 现在进行时的被动语态构成：am / is / are + being + 及物动词的过去分词
Uncle Wang is mending my bike now.→
My bike is being repaired by Tom now.
They are planting trees over there. →
Trees are being planted over there by them.
7. 不定式的被动语态：to + be + 及物动词的过去分词
There are two books to be read. →
There are twenty more trees to be planted.
二、 把主动语态改成被动语态的方法
把主动语态改为被动语态非常简单，可以遵循以下几个步骤：
1. 先找出谓语动词；
2. 再找出谓语动词后的宾语；
3. 把宾语用作被动语态中的主语；
4. 注意人称、时态和数的变化。
例：1. Bruce writes a letter every week. →A letter is written by Bruce every week.
2. Li Lei mended the broken bike this morning.→The broken bike was mended by Li Lei this morning.
3. He has written two novels so far.→Two novels have been written by him so far.
4. They will plant ten trees tomorrow.→Ten trees will be planted by them tomorrow.
5. Lucy is writing a letter now.→A letter is being written by Lucy now.
6. You must lock the door when you leave.→the door must be locked when you leave.
三、 使用被动语态应注意的几个问题：
1. 不及物动词无被动语态。
What will happen in 100 years.
The dinosaurs disappeared about 65 million years ago.
2. 有些动词用主动形式表示被动意义。
This pen writes well.
This new book sells well.
3. 感官动词或使役动词使用省略to的动词不定式，主动语态中不带to ，但变为被动语态时，须加上to 。
例：make somebody do something→somebody+ be +made to do something
see somebody do something→somebody +be +seen to do something
A girl saw my wallet drop when she passed by.→My wallet was seen to drop by a girl when she passed by.
The boss made the little boy do heavy work.→The little boy was made to do heavy work by the boss.
4. 如果是接双宾语的动词改为被动语态时，直接宾语(物)作主语，那么动词后要用介词，这个介词是由与其搭配的动词决定。
He gave me a book.→A book was given to me by him.
He showed me a ticket.→A ticket was shown to me by him.
My father bought me a new bike. →A new bike was bought for me by my father.
5. 一些动词短语用于被动语态时，动词短语应当看作一个整体，而不能丢掉其中的介词或副词。
We can’t laugh him. →He can’t be laugh by us.
He listens to the radio every day. →The radio is listened to by him every day.
The nurse is taking care of the sick man. →The sick man is being taken care of by the nurse.
温馨提示：答案为网友推荐，仅供参考