1、有be的,在be动词后加 not如：Here is a car.否定式 Here is not a car.2、be 动词原形,在这种情况下,必有助动词或情态动词,在助动词或情态动词后加not.如：Now he should be in Beijing.否定式 Now he should not be in Beijing.3、无be动词,必有一般动词构成句子,在动词前加 do not.如：The car hit the door.否定式 The car do not hit the door.这里加的do not 要和动词的时态相一致.