Abstract: The two mechanisms of hydrostatic pressure and pore pressure effects for reservoir-induced earthquake are comparatively simulated and case studied.The results indicate that under the same tectonic stress the water-storage depth for hydrostatic pressure effect needed to induce earthquake is much higher than that of pore pressure effect after water storage in reservoir.As the result of water permeation effect being reinforced in the case of buried fault in reservoir area,the pore pressure effect which induce reservoir earthquake show more sensitivity.The increase of pore pressure after water storage is the major factor of reservoir-induced earthquake.