Underwater integrated navigation is the technical guarantee and foundation for the UUV to complete long endurance underwater autonomous navigation and tasks. The integrated navigation based on INS/DVL/GPS is the current mainstream integrated navigation method for the UUV,which can solve the problem of navigation error accumulation over time and meet the requirements of UUV long endurance underwater navigation. This paper introduces the structure and composition of underwater integrated navigation system,as well as the key technologies. Besides,the initial alignment algorithm,pure inertia solution algorithm,integrated navigation algorithm,DVL calibration algorithm and calibration algorithm have been discussed in detail.