1. 基本方法

将主动语态的宾语变为被动语态的主语，将主动谓语变为被动谓语(be+过去分词)，将主动语态的主语变为by短语(在被动句中用作状语)：He stole our money.→Our money was stolen by him.

【注】(1)若不强调动词执行者，被动语态中的by短语通常可以省略：

The house was built in 1978. 这座房子是1978年建的。

(2) 在转变语态时，要注意保持两种语态时态的一致性：

The students will study the problem.

→The problem will be studied by the students.

A friend of ours is repairing the roof.

→The roof is being repaired by a friend of ours.

2. 双宾动词的被动语态

双宾动词即指带双宾语的动词，它们在变为被动语态时，有以下两种情形值得注意：

(1) 有些双宾动词(如award, buy, give, leave, lend, offer, pay, show, teach, tell等)在变为被动语态时，既可把间接宾语(指人)变为被动语态的主语，而把直接宾语(指事物)保留下来(称为保留宾语)，也可把直接宾语(指事物)变为被动语态的主语，而把间接宾语改为介词to 或for引起的状语(到底用to还是for，与所搭配的动词有关)。

比较：

He gave her some money. 他给她一些钱。

→ She was given some money. / Some money was given to her.

He bought her a watch. 他给她买了一快表。

→ A watch was bought for her. / She was bought a watch.

(2) 有些双宾动词(如bring, do, make, pass, sell, send, sing, write等)通常用直接宾语(指事物)作被动语态的主语，而将间接宾语用作保留宾语(其前根据情况用介词to或for)：

Father made me a doll. → A doll was made for me.

He wrote her a letter. → A letter was written to her.

(3) 有些双宾动词(如answer, deny, envy, refuse, save, spare等)通常用间接宾语(指人)作被动语态的主语，而将直接宾语用作保留宾语：

He answered me that question. → I was answered that question by him.

3. 含有情态动词的被动形式

若主动语态中谓语含有情态动词，在相应的被动语态中通常应保留该情态动词，其结构为“情态动词+be(或be的适当时态形式)+过去分词”：

Everyone must know this. →This must be known by everyone.

请看以下带情态动词被动句实例：

This can’t be done in a short time. 这不是短期内可以完成的。

She may have been sent to work elsewhere. 她可能被派到别处工作去了。

The door must have been locked by my wife. 门一定是我妻子锁的。

The environment should be improved. 环境应当改善。

The second point needn’t be discussed today. 第二点今天不必讨论。