The influencing factors in the process of laminating, hydrogen peroxide solution soaking and cooking stripping on intrinsic viscosity and crystallinity of PET film based on polymer laminate steel are systematically studied by automatic viscosity tester and IR. The result indicates that the intrinsic viscosity and crystallinity of PET film decrease through laminating and cooking stripping process while they increase through hydrogen peroxide solution soaking process. PET is degraded under high temperature or in the presence of water molecules with the result of the decrease in intrinsic viscosity and crystallinity. The degree of polymerization of PET film is increased by hydrogen peroxide with the improvement of the intrinsic viscosity and crystallinity.