The present disclosure relates to beamforming methods and devices. In one example method, an access network device calculates an uplink channel frequency response, calculates a model parameter in a channel frequency response mathematical model based on the uplink channel frequency response and each uplink subcarrier frequency, where the model parameter has reciprocity on uplink and downlink subcarrier frequencies, constructs a downlink channel frequency response based on the model parameter, the channel frequency response mathematical model, and each downlink subcarrier frequency, calculates a beamforming weight for each downlink subcarrier frequency based on the downlink channel frequency response, and performs downlink beamforming on an antenna array based on the beamforming weight for each downlink subcarrier frequency, where the antenna array is a dual-polarized antenna array or a single-polarized antenna array.