A signal transmission method, system and device are described. When measuring a reference signal and determining channel quality, a user equipment (UE) obtains a difference between codeword-to-CSI-RS mapping relationships by using a channel quality measurement model. The UE, using a measurement, calculates an optimized mapping relationship. The UE determines at least one mapping relationship from the mapping relationships, to adjust a codeword-to-CSI-RS mapping relationship of a channel.