Jinsha River Bridge is located along the Lijiang-Xamgyi'nyilha railway on the southeastern Tibet plateau; it is an area with a high prevalence of earthquakes.The bridge abutments were designed to be constructed in river bank slopes,where rocks are controlled by two sets of joint planes that significantly influence the stability of the left bank slope.According to the engineering-geological conditions and the characteristics of discontinuities,strength properties of the rock mass were obtained based on Barton model and direct shear test.Numerical analyses were performed using FLAC3D software to examine the slope's response to seismic loading.Then in order to evaluate the damage trends of the rock mass under the different loading conditions,a calculation model based on the geological parameters and slope stability was simulated and analyzed using the discrete element numerical simulation program UDEC (Universal Distinct Element Code),and the effect of degradation of discontinuities on the slope stability was investigated.The results show that the destruction of rock mass under the gravity,bridge foundation,and seismic load are mainly concentrated within 30 m depth of slope,and the slope under loading may slide along joint planes.In addition,the dynamic analysis by amplification of the input loading indicates that instability occurs to the bank slope at a height of about 200 m,and rock blocks will fail under seismic load.Therefore,to prevent the slope from deformation under the engineering loading and strong earthquakes,the bridge foundation should be strengthened.