Abstract:   In order to solve the problem of large positioning errors when underwater robots work in shallow seas, this paper focuses on the high-precision positioning and navigation system for shallow seawater robots based on GPS／BDS dual-mode combined positioning technology under the condition of shallow sea electromagnetic wave signal attenuation characteristics. In order to compare the positioning performance of the dual-mode positioning system, the GPS and BDS single-mode positioning system is set up. The positioning data processing method using a median filtering algorithm and a Kalman filtering algorithm is proposed to test the dual-mode positioning system and we use filtering data to get the system's positioning performance. The test results show that: the positioning accuracy of the dual-mode positioning system is higher than that of the single-mode positioning system and the application of the median filter and the Kalman filtering algorithm can significantly improve the positioning accuracy of the dual-mode positioning system.