1. 介词短语可以用作表语。如：
Mr. Smith is still in bed. 史密斯先生还在睡觉。
He was already in his sixties. 他已经六十多岁了。
Dinner was at one olock. 一点钟开午饭。
We are out of food. 我们的食物吃完了。
2. 介词短语可以用作状语。如：
The children are playing by the river. 孩子们在河边玩。
They often talk in English after class. 他们经常在课后用英语交谈。
Lets go out for a walk along the river. 咱们到江边散散步。
3. 介词短语可以用作定语。如：
The woman in the room is his wife. 房间里的那个女人是他的妻子。
China is a country with a long history. 中国是一个历史悠久的国家。
介词短语作定语时必须置于被修饰名词之后。如：
the people on the bus 公共汽车上的人
the girl in front of me 我前面的女孩
a woman in black 一个穿黑衣的妇女
a book on sports 一本关于运动的书
a boy with red hair 红头发的男孩
a bird in the tree 树上的鸟
4. 介词短语可以用作宾语补足语。如：
We found her in tears. 我们发现她在哭泣。
The cold kept him in bed for three days. 这次感冒让他卧床三天。
用作宾语补足语的介词短语在相应的被动语态中则为主语补足语：
He was regarded as a hero. 他被看成是英雄。
5. 介词短语可以用作宾语。如：
I saw her from across the street. 我从街对面望见了她。
He goes to work every day except on Sunday. 除星期日外，他每天都上班。
I wont go home until after the exam. 我要等考完后才回家。