Inertial navigation is at the center of underwater navigation due to its passive and autonomous advantages. However, the error of inertial navigation increases with time, and it is difficult to provide accurate navigation information for a long time. In response to this problem, the paper proposes a single-buoy-based underwater acoustic/inertial integrated navigation and positioning method. With the help of the speed and azimuth information of the underwater submersible, the positions of the actual buoy and three virtual buoys, and the relationship with the underwater submersible, using long baseline navigation to realize the navigation and positioning of the underwater submersible. The test results show that, compared with inertial navigation, this method reduces errors and improves positioning accuracy, and it can ensure that the underwater submarine can carry out underwater combat missions during long voyages.