Embodiments of the present invention provide a data transmission method, a base station, and a user equipment. The base station selects a TBS corresponding to a modulation and coding scheme level and corresponding to the number of first physical resource block pairs or the number of second physical resource block pairs, where the number of the second physical resource block pairs is a product of the number of the first physical resource block pairs and a set conversion factor. In this way, a selection of the TBS by the base station is implemented, so that an expected coding rate can be achieved when the base station transmits service data to the UE according to the selected TBS.