This paper presents the results of a study on a joint slope deformation affecting the western slope of the GuangYang highway (YangQuan, China). Fieldwork identified the ongoing deformational process and assisted in defining its mechanisms, evolution and controlling factors. Here we discuss how to use limit equilibrium methods to calculate the behavior of slopes and to use the finite element analysis to evaluate the stability, displacements of slopes and soil-slope stabilization interaction. The finite element method with shear strength reduction (SSR) technique is explained in Phase2D. This method is effective for the prediction of the stability of slope. Based on numerical comparisons between the limit equilibrium methods and finite element method, it is suggested that the finite element method with SSR technique is a reliable and maybe unique approach to evaluate the slope stability. The paper also took into account effectiveness of the large rain and seismic load. The results of the numerical analysis are consistent with the observed slope surface evidence.