1）改变谓语结构。
在系动词be、助动词be，have ／has ／had，will，shall，would，should和情态动词后加not（n't）。若句中没有这些词，则根据谓语动词的原形、第三人称动词形式或过去式而分别在其前面加do not（don't）， does not（doesn't）或did not（didn't），并将第三人称动词或过去式改为原形。如：
He will write the book in two months．→He won't write the book in two months．
We can finish the work this afternoon．→We can't finish the work this afternoon．
He does his homework in the evening．→He doesn't do his homework in the evening．
They put the basket under the tree just now．→They didn't put the basket under the tree just now．
He has seen the film before．→He hasn't seen the film before．
2）用含否定意义的词（如：never，nothing，nobody，none，neither， little，few等）。
①always ／ever→never，and→or。如：
He was always late for school last term．→He was never late for school last term．
They have ever read the book．→They have never read the book．
He can speak Chinese and English．→He can't speak Chinese or English．
②too→not．．．either，already→not．．．yet。如：
He goes to school by bike，too．→He doesn't go to school by bike， either．
He has already finished the work．→He hasn't finished the work yet．
③all→none，both→neither，both．．．and→neither．．．nor，此时，谓语动词仍用肯定形式，但当neither作主语，谓语动词用单数形式；neither．．．nor．．．连接两个主语时，谓语动词应和nor后面的主语保持一致。如：
He knows all of the workers here．→He knows none of the workers here．
Both of the twins are from England．→Neither of the twins is from England．
Both Emma and John have gone to Tokyo．→Neither Emma nor John has gone to Tokyo．
3）当think，believe，suppose等动词后面跟宾语从句时，通常用否定主句谓语动词来达到否定从句谓语动词的目的。如：
I think they can come tonight．→I don't think they can come tonight．
4）当must表示推测，表示“一定、肯定”的含义时，否定句应用 can't。如：
He must be in the room．→He can't be in the room．
