Abstract: In view of the disadvantages of complicated calculation process for the current methods of stability analysis of earth slopes,a simple and convenient graphical method is established, taking many main factors into consideration, such as rock characteristics , topography, underground water condition, water content of soil and earthquake intensity etc. The simplified Bishop′s method is used to induce a dimensionless equation, and a concise graph is obtained by systematic calculation using relevant computer programs. Also, the effect of earthquake intensity, strength parameters, coefficient of pore pressure and other parameters are analyzed. The result show that, the slide area extends with the increase of earthquake intensity, pore pressure , cohesion of soil , whill it decreases with the increase of angle of internal friction φ .