The present disclosure relates to modulation methods. One example method includes performing distribution matching (DM) encoding on N1 first bits to obtain N2 first symbols, determining N4 to-be-phase-modulated symbols whose signal powers are equal to a preset signal power from the N2 first symbols, performing phase modulation on the N4 to-be-phase-modulated symbols based on N3 second bits to obtain N4 second symbols, performing binary labeling (BL) encoding on the N4 second symbols and N2-N4 first symbols to obtain N5 BL encoded output bits, performing forward error correction (FEC) encoding on the N5 BL encoded output bits to obtain N6 FEC redundant bits, and performing quadrature amplitude modulation (QAM) mapping based on the N6 FEC redundant bits and the N5 BL encoded output bits to obtain N2 target QAM signals.