[en] An ultra high molecular weight polyethylene was irradiated with the electron beam at dose levels ranging from 100 kGy to 1MGy. The microstructures of the irradiated samples were characterized by FTIR, gel fraction measurement, DSC and small and wide angle X ray scattering. For the mechanical properties, a static tensile test and creep experiment were also performed. The cross-linking and the crystal morphology changes were the main microstructural changes to influence the mechanical properties. It was found that 250 kGy appeared to the optimal dose level to induce cross-links in the amorphous area and recrystalliztion in the crystal lamellae. At doses above 250 kGy, the electron beam penetrates into the crystal domains, resulting in cross-links in the crystal domains and reduction in the crystal size and crystallinity. The static mechanical properties (modulus, strength) and the creep resistance were enhanced by the electron beam irradiation. The stiffness rather correlated with the degree of cross-links, while the strength with the crystal morphology. (author)