as...as sb could 这个一般用在句尾,做动词的补语,表示尽可能adj./adv.的去做某事例子 she is running as fast as he could.而can是情态动词 经常放在谓语动词前面构成整体的谓语结构参考：can（1）“can”表达能力...对不起，我是说as as sb. could 和 as as sb. can是否有差别as as sb. could 和 as as sb. can非要说却别的话前者用于过去时，后者用于现在时