Abstract: From the analysis of the characteristics of sonar signal processing, a new achitec-ture called cascade link achitecture to implement large digital sonar system with general processors and special signal processors is proposed. This achitecture is very suitable for large mult-chanel sonar signal processing. The basic elements, including data bus protocal, data transmition, control unit, basic processing cell are discussed. Last, a regular step to design a digital sonar using this achitecture are suggested.