Polypropylene film is the most widely used dielectric material in HVDC capacitors. As the voltage level and transmission capacity of the power system increase, the dielectric properties of polypropylene film become more demanding. In recent years, researchers have studied the modification methods of polypropylene film to improve its breakdown field strength and energy storage density under operating conditions, and to reduce its dielectric loss. This book comprehensively reports the relevant research on polypropylene film for HVDC capacitors. The book details the application background, fundamental properties and related theories of polypropylene dielectrics. The relationship between the microstructure and the dielectric properties of polypropylene films is described, and the insulation failure mechanism of polypropylene is discussed. The modification methods of polypropylene energy storage media including ash washing, molecular chain structure regulation, aggregation structure regulation, nanoparticle doping, polyphenyl ring compound modification, cycloolefin copolymer blending and interfacial molecular regulation are reviewed. The effects of high temperature and strong magnetic field on the dielectric properties of polypropylene films are discussed and the high temperature and strong magnetic field resistant polypropylene dielectrics are presented.The book contains the dielectric constant, conductivity, breakdown field strength, energy storage density and other relevant graphs and data of modified polypropylene film under different operating conditions, which clearly explains the improvement effect of various modification methods on the dielectric properties of polypropylene film. This book provides a comprehensive reference for the research of polypropylene film for HVDC capacitors. It can help students, researchers and technicians in related industries to understand the insulation failure mechanism of polypropylene film and make readers understand the latest modification methods to improve the dielectric performance of PP films.