The invention discloses the structure and working principle of an information source channel joint codec and its codec parameter optimization design method based on vector quantization. The codec in the present invention is divided into encoder and decoder two parts, and encoder is by the input information source message vector buffer, encoding index generator, channel signal output unit, channel signal power and other encoding parameter memory, reconstruction information source Composed of message memory and coded channel signal memory; decoder consists of input channel signal vector buffer, decoding index generator, reconstructed source message output unit, decoded channel signal memory and reconstructed source message memory. The codec can directly encode a channel-optimized K-dimensional channel signal that strictly meets the requirement of average transmit power from L-dimensional source information, and realize source bandwidth compression or expansion. The codec has simple structure, low coding and decoding complexity, and strong versatility. The codec has excellent performance and has the characteristics of flexible degradation and flexible improvement, especially suitable for multi-user and time-varying channel applications.