Abstract: Traditional landslide hazard assessments often rely on indirect characteristics, such as slope surface displacement or deformation rate, but seldom directly utilize the physical properties of the sliding surface itself to assess the risk of landslides. In this paper, a slope hazard assessment theory and method based on the residual friction of the sliding surface are developed. The basic process is as follows: Firstly, InSAR technology is used to extract the time series deformation data of the landslide. Secondly, the spatial and temporal evolution characteristics of the slope along the sliding surface are obtained by inversion under the constraint of slope surface deformation. Further, the residual friction coefficient and stable friction coefficient of the slope are calculated according to the law of velocity friction attenuation. The temporal and spatial variation of the stable friction coefficient of the sliding surface is analyzed, and then the risk of landslides is quantitatively evaluated. This paper selects the Pangcun Landslide in Longzi County, Shannan City, Xizang, as the research object and applies the proposed theory and method to obtain the stable friction coefficient of the multi-stage sliding surface of the Pangcun Landslide. The results show that although the stable friction coefficient of the sliding surface will fluctuate periodically with the season, it generally shows a significant downward trend, developing from the trailing edge of the landslide to the leading edge of the landslide. At the same time, it is preliminarily speculated that when the stable friction coefficient of the sliding surface is less than 0.4, the landslide may enter a critical sliding instability state. The method of friction residual and landslide risk assessment using InSAR deformation proposed in this paper can realize a relatively convenient and quick quantitative evaluation of the landslide state. It has a relatively low cost and can provide a meaningful scientific reference for monitoring, early warning, and risk assessment of wide-area landslide disasters.