A waveform selection method and a device are disclosed. The method includes: obtaining an uplink signal sent by a terminal device; measuring, based on the obtained uplink signal N corresponding signal-to-noise ratios when the terminal device sends the uplink signal by using N ranks; calculating a first modulation and coding efficiency corresponding to each of the first signal-to-noise ratios; calculating, based on the first modulation and coding efficiency corresponding to each first signal-to-noise ratio, a second modulation and coding efficiency corresponding to each rank; selecting a target modulation and coding efficiency from second modulation and coding efficiencies corresponding to the N ranks; determining a target modulation and coding scheme; determining a target modulation scheme based on a target rank and the target modulation and coding scheme; and determining, based on the target modulation scheme and the target rank, a waveform type for the terminal device.