一是時態不能改變;二是變為被動語態后，謂語動詞要和被動語態的主語在人稱、數上保持一致。還要作如下變動：把主動語態的賓語變為被動語態的主語;主動語態的主語放在by的后面，組成介詞短語，再把這個介詞短語放在被動語態的謂語動詞之后。在動作的執行者無須說明或不必要強調時，by短語可以省略。例如，

They will open a new supermarket there soon. 他們很快將在那里開辦個新超市。

A new supermarket will be opened there soon. 一個新超市不久將在那里開辦。

The doctor gave two lectures in English. 那位醫生用英語講了兩次課

Two lectures were given by the doctor in English. 由那位醫生用英語講了兩次課。

Somebody has warned us to be careful of rats. 有人警告我們要當心老鼠。

We have been warned to be careful of rats. 我們受到警告，要當心老鼠

如果主動語態有兩個賓語(直接賓語和間接賓語)，變為被動語態時，可將其中任何一個賓語變為主語，另一個不變。但較常見的是將間接賓語變為被動語態的主語。

The reporters asked the president some questions. 記者們問了總統一些問題。

The president was asked some questions by the reporters. ( 變間接賓語為主語)

Some questions were asked the president by the reporters. (變直接賓語為主語)

We have given him a job. 我們已給了他一個工作。

He has been given a job. (變間接賓語為主語)

A job has been given (to) him. (變直接賓語為主語)