The code of elastic half-space （Okada） is often used to calculate the coseismic deformation. However, this code can not consider the effect of the stratification of rock, gravity and viscosity on deformation. In this paper, with the help of Wang＇s code （PSGRN/PSCMP） , considering the level / tilt strike-slip and dip-slip several situations, the influences of role of stratification and gravity on numerical simulation of co-seismic deformation field are discussed, and a comparison with the results of half-space model without considering the stratification of rock and gravity is done also. The result shows that gravity has little influence on coseismic deformation; visco-elastic stratification has larger influence on it than gravity ; better result could be got undoubtedly if considering both role of stratification and gravity. Magnitude of Viscosity had a very important influence on the shape and amplitude of postseismic deformation curves, and that it is very necessary to consider the role of crust viscosity if the problem deals with postseismic deformation.