⑴含有使役动词（make /let /have）或感官动词（hear ,see, listen to ,look at ,find ,watch, feel等）的句子，在主动语态中这些词后常跟不带to的动词不定式，但是在改成被动语态时，则一定要把省去的to再加上去，另外help这一个词在主动语态中后面的动词不定式可以带to,也可不带to, 但在被动语态中也必须把to加上去。
例：①Mother often makes me do homework.
→I am often made to do homework by mother.
,pass ,show ,buy, tell等动词常常带有两个宾语（双宾语：直接宾语和间接宾语），改为被动语态时，两个宾语可以选其中任一个作主语。如果直接宾语被提前作主语，那么间接宾语（一般是人）前要加相应的介词to/for。
①She gave me a book.= She gave a pen to book.
→I was given a book by her.
→A book was given to me by her.
②My father bought me a MP3.= My father bought a MP3 for me.
→I was bought a MP3 by my father.
→A MP3 was bought for me by my father.
例：①We call him Xiao Ming.
主 谓 宾 宾补
→Ｈe is called Xiao Ming by us.
②He found the novel very interesting.
→The novel was found very interesting by him.
1. 没有被动语态的词， 表示状态或特征的及物动词如 cost, fit, have, suit等没有被动形式，另外，像happen = take place, break out(爆发)，break down(坏了) result from(缘于)，belong to, consist of等只用主动语态，而不用被动语态
2. 不及物动词或动词短语无被动语态: appear, die ,disappear, end (vi. 结束), fail, last, lie, remain, sit, spread（传播）, stand, come true, fall asleep, ...
3. 大多数系动词：be , feel (摸起来)，sound(听起来)，smell(闻起来)，taste（尝起来），look(看起来)，等词无被动语态，它们的主动形式表示被动意义。
例：①The shirt feels very soft. 这件衬衣摸起来很柔软。
②Many changes have taken place in our country.