与助动词或情态动词do, does, did, shall, will, should, would, may, might, have to, must, need, ought to等一起构成谓语的动词时,要用原形。在现行的初中英语正橡含教材中,大致有以下十种情况使用动词原形:Do you like English? 你喜欢英语吗?May I use your telephone? 我可以用你的电话吗?We must study hard and make progress every day. 我们如基必须好好学习,天天向上。Shall we tell her to wait? 我们要不要告诉她等一下?2.祈使句的谓语动词,要用原形。如:Close the door behind you, please. 请随手关上门。Don't make a noise. 别吵闹。Let's live in peace and friendship. 让我们生活在和平和友谊之中。3.感官动词look at, see, watch, notice, listen to, hear, feel等的宾语与其补足语构成逻辑上的主谓关系,表示动作的最后结果或全过程时,作宾语补足语的动词要用原形。但改成被动语态要带to。如:I saw the train come into the station. 我看见火车进站了。I heard a letter drop.(A letter was heard to drop.) 我听到信掉了下去。4.使役动词let, have, make后的宾语与作宾语补足语的动词构成逻辑上的举笑主谓关系时,这个动词要用原形。但改成被动语态要带to;let后的动词可不带to, 如:He let Jack lead the way. 他让杰克在前面带路。Have him send the letter. 叫他把信送去。His jokes made us all laugh. 他的笑话使我们都大笑起来。Everyone must be made to know nobody should break the law.应使每个人都知道,谁也不得违法。5.两个以上的并列不定式用and或or连接起来,第二个不定式常省去to。如:Let's go and play football.我们去踢球。It is fun to jump into pool or go swimming in a river in summer.在夏天跳进游泳池或江河里去游泳是很有趣的。6.在why not…和why…句型中,not和why后直接跟动词原形,构成反问,表示“建议、劝告、责备或提醒”等。如:Why not use my bicycle? 为什么不用我的自行车呢?Why waste so much money? 为什么要浪费那么多钱呢?7.动词help后是复合宾语,其宾语补足语由动词充当时,这个动词前带to或不带to都可,但在被动语态中必须带to。如:She helped me (to) clean the room.(I was helped to clean the room byher.)他帮我打扫房间。8. do ,does[1] ,did与动词原形连用,以加强语气,不但可以用在祈使句中,而且也可用在一般现在时和一般过去时的肯定陈述句中。如:Do be careful! 一定要当心!She does look nice today. 她今天看起来的确漂亮。I did think he was wrong. 我的确认为他错了。9.不定式作介词but和except的宾语,当其前有实意动词do时,后面的动词不定式要省略to。如:Jack had nothing to do but/except watch TV. 杰克除了看电视外无事可做。10.在一些固定的句型中,如had better(最好),would rather (宁愿),would rather…than…(宁愿…而不)等后面的动词要用原形。如:You had better have a good rest. 你最好好好休息一下。He would rather go to work by bike. 他宁愿骑自行车去上班。As a revolutionary,he would rather die with his head high than live with his knees bent. 作为革命者,他宁愿昂首而死,而不愿屈膝求生。