The construction of the GPS water vapor auto processing system based on GAMIT, the system design concepts, and the specific implementation procedures are described. The accuracy check and error analysis of the GPS water vapor, the methods of the quality control 〖JP2〗and fault processing, and the application effectiveness in practical work are also discussed. The results show that the system can process the observation data from GPS stations to get atmospheric water vapor for weather analysis and forecasting. The system is highly automatic and easy to use, demonstrating great potential for operational use.