The γ-radiation effects on polycaprolactones with different molecular weight were investigated. It was concluded that PCL was able to be radiation cross-linked, and the dose of gelation decreased with the increasing of molecular weight. The relation between sol fraction ,http://notExist.jpg,http://notExist.jpg,http://notExist.jpg, and the reciprocal of radiation dosage (1/,D,) meets Charlesby-Pinner formula. This indicates that the radiation cross-linking of PCL follows the theory of random cross-linking. Mechanical properties of radiated PCL were determined. The tensile strength and elongation at break declined with increasing doses, but the dose effects on tensile strength of high molecular weight PCL were as severe as low molecular weight PCL. Dynamic mechanical analysis showed that the heat distortion resistance and the temperature of abrupt drop point for tensile modulus E′ increased markedly with the irradiation dose.