Sensitizing effects of polyfunctional polyester acrylate (PEA) on radiation cross-linkage of PCL were studied in this paper. Influences of the added amount of PEA, number of the functional groups, and irradiation dose on dynamic mechanical properties of the cross-linked PCL samples were investigated. It was concluded that efficiency of radiation cross-linking of the PCL samples could be improved markedly after applying the polyfunctional naterials. The more the number of the functional groups and the more amount of the functional groups, the more the gel content and the more distinctive radiation cross-linking effects. Mechanisms of the enhanced radiation cross-linking effect were discussed. It appeared that the double bonds broken from molecule chains of the polyfunctional naterials s by the ionizing radiation had been of help to the cross-linking reactions. In addition, it was found that the radiation cross-linking of PCL in presence of the polyfunctional naterials could be described by the Chen-Liu-Tang relation, rather than the classical Charlesby–Pinner equation. The DMA analysis indicated that the radiation cross-linked PCL had higher heat deformation temperature with a wide rubbery state plateau.