動(dòng)詞do在句中的作用可以概述為四句十二字：“做”實(shí)義，助動(dòng)詞，替前文，強(qiáng)語(yǔ)氣。

　　作用一：實(shí)義do

　　do作實(shí)義動(dòng)詞時(shí)，有do, does, did, done, doing五種形式，還有及物、不及物之分。如：

　　1、 vt. “做；研究；整理；完成”。如：

　　①The old man does an hour of sport every day.

　　②She did her homework at home last night.

　　③Mother was doing the cooking when I reached home.

　　④Have you done the exercises yet?

　　2.、vi. “行動(dòng)；工作；進(jìn)展；足夠”。如：

　　①Kate does very well in her Chinese.

　　②How do you do?

　　③Well done!

　　④That will do.

　　作用二：助動(dòng)do

　　do作助動(dòng)詞時(shí)，只有do, does, did三種形式，無(wú)詞義，限用于含行為動(dòng)詞的一般現(xiàn)在時(shí)和一般過(guò)去時(shí)兩種時(shí)態(tài)的否定句和疑問(wèn)句中。如：

　　①They don't have any tickets for tonight's concert.

　　②Kate stayed at home last night, didn't she?

　　③How many books does the library have?

　　④She doesn't do the washing in the evening.

　　作用三：替代do

　　為避免動(dòng)詞的重復(fù)，使語(yǔ)言簡(jiǎn)練，常以do, does, did替代前文所用的行為動(dòng)詞。如：

　　①Tom runs much faster than you do.

　　②-Lucy, can you get some more tea, please?

　　-Sure. I'll do it right away.

　　②-Who broke the cup?

　　-Mimi did.

　　③-I like bananas.

　　-So does he.

　　作用四：語(yǔ)氣do

　　為突出感情色彩，do常用于祈使句、強(qiáng)調(diào)句和倒裝句中，以加強(qiáng)語(yǔ)氣。如：

　　①Do be careful.

　　②Don't tell a lie.

　　③He did come.

　　④-You often go to the park.

　　-So we do.