助动词就是协助主要动词构成谓语的动词.助动词本身没有词义,不可单独作谓语,只能和别的动词一起构成谓语,表示时态、语态、语气等,或表示疑问或否定.常用的助动词有be, do, does, did, have, has, shall, will, would等.
（1）助动词be主要用法
a、be+现在分词构成进行时态.如：
He is listening to the radio.他在听无线电广播.
What were you doing this time yesterday afternoon?昨天下午这个时候你在干什么?
b、be+过去分词构成被动时态.
He is invited to the party.他得到邀请参加这个聚会.
The letter was received this morning.这信是今天上午收到的.
c、be+动词不定式表示计划好了的将来动作.如：
The meeting is to take place on Monday.会议将在星期一举行.
（2）助动词have的主要用法
have+过去分词构成完成时态.如：
I have finished my work.我已干完了活儿.
I had written the letter befor you came.在你来之前我已写好了信.
（3）助动词do的主要用法
a、帮助主要动词构成疑问句和否定句.如：
Do you do morning exercises every day?你每天做早操吗?
She didn't come yesterday.她昨天没有来.
b、构成否定祈使句.如：
Don't be to rude.不要这么无礼.
Don't worry about that.不要为这事操心.
c、加强陈述句和祈使句的语气.如：
I do work hard.我的确是努力工作的.
Do be careful!一定要细心!
d、用于避免主要动词的重复出现.如：
Do you do somke? Yes ,I do.你抽烟吗?是的,我抽.
I went to concent yesterday.SO did he.我昨天去听音乐会了.他也去了.
e、构成倒装句.如：
Never dia he go here again.他再也没去过那里.
Only then did I understand what she meant.只是到那时,我才懂得她是什么意思.
（4）助动词shall和will的主要用法
shall/will +动词原形构成将来时态.shall用于第一人称（I,we ),will用于第二、三人称,也可用于第一人称.如：
I shall/will arrive tomorrow.我将于明天到达.
We shall/will beglad to see you .我们将很高兴见到你.
He will be twenty-two next week.他到下星期有22岁了.
They will leave for shanghai tonight.他们今晚动身去上海.
（5）助动词should 和would的用法
should /would+动词原形构成过去将来时.
He told us where we shoulid /would have the basketball match.他告诉我们将在什么地方举行篮球比赛.
