The early identification and monitoring of landslides is of great significance to disaster assessment, mitigation, and prevention. Although interferometric radar technology can achieve large-scale and infinite-point with high-precision surface deformation monitoring, when the real deformation direction is different from the radar line of sight direction, its detection sensitivity will be reduced. We take the Xishan landslide group in Qinghai Province as the research object and use the ascending and descending Sentinel-1A data from January 9, 2019, to April 9, 2020, to reconstruct the slope direction velocity field based on conversion relationship; and using the mutual verification of ascending and descending orbit can obtain accurate and reliable unstable slope range. Adopting fusion of ascending and descending orbit data, with the decomposition of the deformation information of the Xishan landslide group, the vertical and east-west deformations of the slope are extracted, and the stability of the slope is analyzed based on the deformation characteristics of the landslide, topography, and site survey results.