A stereo signal encoding method includes obtaining indication information of an encoding mode of a residual signal of a current frame, where the indication information includes at least one of an encoding status of a residual signal of a previous frame, a value of an updating manner flag for a long-term smooth parameter of the current frame, or a value of a status change parameter of the current frame relative to a stereo signal of the previous frame, and determining the encoding mode of the residual signal of the current frame based on the indication information of the encoding mode of the residual signal of the current frame, where the encoding mode indicates whether to encode the residual signal of the current frame.