A data transmission method for data transmission, including obtaining, by a network device, a quantity of physical resource blocks (PRBs) that are occupied by first data carried in a first subframe, where the quantity of PRBs that are occupied by the first data carried in the first subframe is preconfigured, or may be determined by the network device or user equipment, determining a first transport block size (TBS) according to the quantity of PRBs that are occupied by the first data carried in the first subframe, performing, according to the first TBS, modulation and coding on the first data carried in the first subframe and first data carried in a second subframe, and sending the first subframe and the second subframe to the user equipment.