Abstract: In order to evaluate accurately the stability of slopes of rock debris and soil,the integral stability coefficient of a debris and soil landslide was computed and its stability was analyzed through the data collection,arrangement and analysis,site engineering-geological investigation and exploration and indoor and outdoor physical mechanics tests and by adopting the 3D contact elastic-plastic FEM algorithm.When using the 3D elastic-plastic contact FEM strength reduction method to compute the stability coefficient of debris-soil landslides,the space effect of the sliding mass may be considered in order the calculation results to be more accurate.During the deformation,disintegration and failure of debris-soil landslides,in space the plastic strain of the sliding mass and shear strength of the rock or soil mass on a sliding plane are different.The method for computing the stability coefficient of the debris-soil landslide of a 2D section by extracting the contact frictional stress on the sliding surface on the basis of the computation result by the 3D elastic-plastic contact FEM algorithm is relatively suited to the stability analysis and evaluation of this type of landslide and can reflect the actual state of the landslide relatively objectively and accurately.