A data transmission method and apparatus are provided, which can improve a throughput rate of a system, and improve data transmission performance and user experience. The method comprises determining a target bit sequence. In the system state, a peak-to-average power ratio PAPR corresponding to the target bit sequence is less than a PAPR that corresponds to a bit sequence corresponding to the data length of the target data. The method comprises adding the target bit sequence to length bits that are in a legacy signal field of a target preamble, and performing transmit power enhancement processing on a legacy short training field, a legacy long training field, and the legacy signal field that are in the target preamble according to the transmit power amplification limit.