According to the receiving array size, the underwater acoustic positioning system can be divided into three positioning systems: long baseline (LBL), short baseline (SBL) and ultra-short baseline (USBL). Acoustic detection and positioning technology based on ultra-short baseline is the most effective means to collect and transmit information, and is an effective way to solve the positioning accuracy of underwater vehicles. In this paper, the short baseline positioning and navigation system is studied deeply, and an underwater acoustic positioning algorithm based on extended Kalman filter is proposed. By fusing the information of pressure gauge, digital compass and accelerometer of the robot, the positioning accuracy is improved and the influence of underwater channel multipath effect on the system is reduced.