Position and azimuth determining technology is one of the main technologies for deep ocean work. The authors propose a research method based on ring laser gyros, which can determine position and azimuth of deep-sea submersibles. According to the method, a set of analysis programs are designed, with which the attitude, velocity and position error are simulated and analyzed in detail. A 72-hour position and azimuth determining experiment has been carried out, which shows that the error of pitch and roll angle is below 0.006°, the azimuth error is below 0.035°, the velocity error is below 0.9 m?s–1, and the position error is below 29.9 km. The experiment results agree with the analysis results, which indicate that the research method is valid. Compared with position and azimuth determining system based on dynamically tuned gyroscopes, this new system has higher precision and better reliability.