This application provides a stereo
signal encoding method and apparatus. The encoding method includes: determining a residual
signal encoding parameter of a current frame of a stereo
signal based on downmixed signal energy and residual signal energy of each of M sub-bands of the current frame, where the residual
signal encoding parameter of the current frame is used to indicate whether to
encode residual signals of the M sub-bands, the M sub-bands are at least some of N sub-bands, N is a positive integer greater than 1, M ≤ N, and M is a positive integer (301); and determining, based on the residual
signal encoding parameter of the current frame, whether to
encode the residual signals of the M sub-bands of the current frame (302). According to the encoding method, high-frequency
distortion of a decoded stereo signal can be reduced as much as possible while a spatial sense and sound-image stability of the decoded stereo signal are improved, thereby improving encoding quality.