Abstract: The calculation deals with a rectangular plate with central crack under tensile pulsating loads in y-direction. The stress and strain distributions and the size of plastic zone ahead of the crack tip are determined by means of elastoplastic FEM. The material of the plate is assumed to be perfectly elastoplastic. Average rigidity method and first order self-correction method are used respectively in the calculation. The strong and weak points of both the methods are discussed.The calculation demonstrates that there is a high compressive residual stress ahead of the crack tip when a peak of overload is followed by pulsating loads. The size of the intrinsic plastic region becomes smaller. This would cause retardation of the fatigue crack propagation rate. Moreover, The COD increases with the peak overload. This may accelerate the growth of the crack. It is shown wrong that the peak overload should be as large as possible. There must be a limit on it.The results of the calculation agree well with data of H. Miyamo-to, but the machine time is lessened.