need做情态动词时没有时态的变化,过去式也是need.后面接动词原形.如: I need write a letter yesterday. Need he answer it then? Yes,he need. No,he needn't. 情态动词need表示对过去的推测时常和现在完成时连用.如: You needn't have hurried.你当时不必这么匆忙. need做实义动词(行为动词)时,过去式是needed.后面接to do.如: I needed to write a letter yesterday. Did he need to answer it then? Yes,he did. No,he didn't.