Abstract: Continuous wave(CW) is commonly used in traditional underwater acoustic tracking & positioning system, and CW signal is easy to be implemented.However, it has many disadvantages, such as sensitive to multipath interference, multiple-access impossible, unable to solve the contradiction between range and resolution, and low security.SS(spread spectrum) technology can overcome such disadvantages, and is used widely in communication.In shallow water area, DS-SS is the more suitable SS technology for underwater acoustic channel.A DS-SS model is discussed and the simulation about the performance of anti multipath interference, multiple-access, and anti tone interference has been done.Simulations show that the model has good performance and potential applications.