A high dam with 185 meter above sea level will be built for the Three Gorges reservoir, which will accommodate water of 39.3 billion cubic meters in maximum and its impoundment will reach up to 175 meters in height. The local stress status, medium propriety and regional stress field in and around the reservoir will vary with the impounding and water fluctuation in the reservoir which will probably induce seismicity. In order to detect crustal deformation, tectonic fault displacement, sink of reservoir basin in the area and reservoir-induced seismicity, a monitoring system is set up. The paper introduces the study on monitoring in Three Gorges, of the Yangtze River.