Proceeding of the Joint International Symposium on Deformatuon Monitoring. 2-4 November, 2011. Hong Kong. China. Report. To automatically and continuously monitor the deformation of Shanxi Xilongchi Pumped Storage Power Station, GNSS(Global Navigation Satellite System) Continuously Operating Reference System (CORS) was established. A DAM Deformation Monitoring System (DDMS), which consists of 4 parts, was developed. The system consists of two reference stations and five monitoring stations. We designed a star topology network architecture and TCP/IP(Transfer Control Protocol/Internet Protocol) protocol for real-time data stream transmission. A data processing software with the function of quality control, coordinates estimation and transformation, accuracy evaluation and session time setting was realized. We can also analyze the stability of fiducial stations, extract deformation, and display deformation behavior of the dam in the system. One-year operating results demonstrate that DDMS has higher stability.The probability of providing effective solutions is up to 98% without data loss.And 2-hour-session solution can achieve 1.2mm, 0.9mm, 2.2mm at north-south, east-west and vertical component of station respectively. The accuracy can be improved to 0.8mm, 0.7mm, and 1.5mm respectively while the session time extend to four hour. It is concluded that the system can provide a technically advanced and cost-effective infrastructure for dam deformation monitoring analysis.