Abstract: The crystal structure of polyethylene which is irradiated by γ-rays in heir melting states was studied by means of small angle X-ray scattering(SAXS) method. The results show that the more radiation dose irradiating PE, the smaller the lamellar thinkness is. And consequently,the crystallization of flexible chain polymers from the rubbery state or from the melt does not proceed by chain folding, the solidification model of fischer is a much more appropriate physical picture for the crystallization process from molten state.