Abstract: The radiation effect of powdery HDPE was studied,and was shown to be different behavior from sheet or film HDPE.Some factors affecting radiation grafting in solid state powdery HDPE like dose,dose rate,monomer kinds,were investigated in detail.The characteristics of grafted HDPE such as melting temperature,crystallinity,decomposition temperature and decomposition activation energy were analyzed.Compared to the ungrafted HDPE, the grafted HDPE has better cohesive force and flexibility.The influence of various groups on cohesive force and flexibility was studied.