Abstract: The traditional polypropylene (PP) film has the problems of low breakdown field strength and high conductivity loss under high temperature and strong electric field environment. We proposed a new modified method based on γ-ray irradiation for polypropylene film, and studied the effects of irradiation dose and sensitizer on the dielectric properties of polypropylene films.Polypropylene films containing sensitizers such as trimethylolpropane triacrylate (TMPTA) and pentaerythritol triacrylate (PETA) were prepared. Total irradiation dose of 0, 5 and 10 kGy were carried out under ⁶⁰Co-γ-ray source. The molecular chain and aggregation structure of irradiated cross-linked polypropylene film were analyzed, and the influences of cross-linked structure on the conductivity and breakdown field strength of polypropylene film under high temperature and strong field were studied. The results show that high energy radiation can form a three-dimensional network structure in the polypropylene film, enhance the force between molecular chains and thermal stability, effectively inhibit the carrier transport in polypropylene, and significantly improve the high-temperature dielectric properties of polypropylene film. At 115 ℃, the conductivity of the modified polypropylene film with the crosslinking degree of 25.04% is decreased by 64.2%, the breakdown field strength is increased by 16.6%, and the maximum theoretical energy storage density reaches 3.78 J/cm³. It is revealed that irradiation crosslinking modification can effectively improve the high temperature dielectric properties of polypropylene films.