A method for re-rating a prepaid user is proposed in the present invention. Compared with prior prepaid systems, the present invention introduces new functional entities, i.e. a re-rating management apparatus and an offline charging apparatus, and enhances the existing functional-entity, i.e. the online charging apparatus. The online charging apparatus rates call detail records comprised in an received online charging request to generate rated call detail records, and sends—the rated call detail records to the re-rating management apparatus; periodically backs up account profile, and sends the backed up account profile to the re-rating management apparatus; the re-rating management apparatus triggers re-rating, sends a re-rating request to the offline charging apparatus; the offline charging apparatus generates re-rated call detail records after re-calculating, the call detail records, and sends the re-rated call detail records to the re-rating management apparatus; and the re-rating management apparatus updates account profile in accordance with the re-rated call detail records, and sends the updated account profile to the online charging apparatus. By using the method of the present invention, the re-rating function can be implemented for the prepaid user without affecting the real-time use by the prepaid user, and the problems occurring in the convergence of a prepaid charging system and a postpaid charging system can be solved.