Various embodiments provide a resource allocation method and an apparatus. In those embodiments, a terminal device obtains a first parameter indicating a maximum service data volume to be provided by an access network device for a first service in a first time length; and determines, based on the maximum service data volume, a resource of a media access control protocol data unit MAC PDU, the resource being occupied by buffered data of the first service. In those embodiments, the terminal device determines, based on the maximum service data volume of the first service, the resource of the MAC PDU. Compared with a conventional method, the maximum service data volume of the first service is considered. This helps improve reasonableness of allocating the resource of the MAC PDU to the data of the first service.