Ascending and descending time series interferometric synthetic aperture radar (InSAR) technology has been used to identify and monitor landslide and deformation of reservoir slopes of a hydropower station on the Jinsha River. It has been found that the landslide areas and deformation trends identified by the approach agree with those of past geological investigation and global position system (GPS) monitoring, which shows that InSAR technology is reliable and useful for landslide monitoring of reservoir slope in mountainous region. Results show that the deformation rate of Xinjian landslide is relatively larger than that of others, with the maximum rate reaching 198.90 mm/a. In the same monitoring period, the root mean square error of the cumulative deformation difference between InSAR and GPS in the line of sight is 39.10 mm, and the maximum difference is 56.65 mm at the XJ17 point. The analysis of the correlation among landslide deformation,daily precipitation and reservoir water level changes shows that the deformation of the Xinjian landslide changes in a periodic step style, which has a lag after heavy rainfall or sudden changes in the reservoir water level. The research can provide a new effective method for landslide monitoring and hazard identification of reservoir slopes in mountainou areas.