The influences of UV-photocrosslinking on crystallite structure and nonisothermal crystallization kinetics of polyethylene (PE) were investigated by optical microscope (OM) and differential scanning calorimetry (DSC) at different cooling rates, respectively. The observation of crystallite structure showed that, due to crosslinking of molecular chains of PE, the PE spherulites grow more imperfectly with increasing gel content. The Avrami analysis modified by Jeziorny was applied to describe the nonisothermal crystallization process of virgin PE and photocrosslinked PE (XLPE) samples. The values of half-time of crystallization t(1/2) and the parameter Z(c) showed that the crystallization rate increased with increasing cooling rates for both XLPE and virgin PE, but the crystallization rate of XLPE is lower than that of virgin PE at the same cooling rate. The activation energies were estimated by the Kissinger method, and the values were 176.7 and 197.1 kJ/mol for virgin PE and XLPE, respectively, indicating that UV-photocrosslinking might hinder the overall nonisothermal crystallization process of PE. (C) 2007 Wiley Periodicals, Inc.