Abstract: A method and system for backward compatible multi-channel audio encoding and decoding in sense of the space information maximum entropy is disclosed. The technical solution according to the invention can adopt any existing stereo channel encoding system to encode the multi-channels audio signals, so as to transmit the multi-channel audio signals at the low bit rate as that of the stereo audio signals. More importantly, the existing stereo channel reproducing systems can also decode the audio format that is encoded utilizing the encoding method according to the invention.