"The stress window" in subside fault block of central Hebei before Tangshan earthquake is simulated by means of the planestrain finite element method,Three.questions under study:(1) the relation between high stress area and the direction of principal stress and the value of Young's modulus;(2) the relation between high stress area and the value of principal stress and boundary condition;(3) the appearance of dynamic process and disappearance of stress window effect.