Abstract：3D finite element method is employed in the prediction and calculation of seismic deformation with the parabola model of horizontal displacement distribution，and the seismic deformation of Mogao Grottoes in Dunhuang as a case study. The results show that 3D finite element method is of high precision，being able to control boundary conditions and adjust computation models. The calculated displacements and strains on the ground surface agree，in order of magnitude，with the actual values observed in earthquake. The influence of fault dimension on the result is also studied，which indicates that the calculated value is stable when fault depth is greater than a certain value，and the reliable earthquake deformation with 3D finite element method can be achieved.
