Abstract: A new approach for evaluating the permanent displacement of rock mass slope including planar slide and wedge slide during earthquake was presented,which considered deterioration of slide surface during earthquake.The procedure for putting the method into effect was put forward,and three case histories were studied.It was indicated that the approach was available and reasonable to assess the value of the permanent displacement of rock mass slope.The result reached by traditional Newmark method was too small in general.Traditional Newmark method was only suitable to evaluate the rock mass slope with small permanent displacement during earthquake.