A multi-channel signal encoding method and an encoder, where the encoding method includes obtaining a multi-channel signal of a current frame, determining an initial multi-channel parameter of the current frame, determining a difference parameter based on the initial multi-channel parameter of the current frame and multi-channel parameters of previous K frames of the current frame, where the difference parameter represents a difference between the initial multi-channel parameter of the current frame and the multi-channel parameters of the previous K frames, and K is an integer greater than or equal to one, determining a multi-channel parameter of the current frame based on the difference parameter and a characteristic parameter of the current frame, and encoding the multi-channel signal based on the multi-channel parameter of the current frame. Hence, the method and the encoder ensure better accuracy of inter-channel information of a multi-channel signal.