A data transmission method includes generating a physical layer data frame, where the physical layer data frame includes data on which probability non-uniform modulation is performed and indication information, where the indication information indicates demodulation parameters for performing probability non-uniform demodulation on the data, where the demodulation parameters include a modulation scheme for probability non-uniform modulation, a modulation order for probability non-uniform modulation, and at least one of a probability of each constellation symbol on which probability non-uniform modulation is performed, or a mapping relationship between each constellation symbol on which probability non-uniform modulation is performed and a bit stream, sending the physical layer data frame to a receive end, receiving the physical layer data frame, determining the demodulation parameters based on the indication information, and performing probability non-uniform demodulation on the data based on the demodulation parameters.