Abstract: Metalized film capacitors are widely used as the core equipment of advanced energy systems such as high-voltage direct current (HVDC) transmission systems due to their excellent insulation characteristics and self-healing properties. The insulating dielectric polypropylene film is an important factor restricting the safe and reliable operation of capacitors. In this paper, we systematically sort out the research progress of insulating dielectric for HVDC capacitors, and summarize the current risks and challenges faced by the films based on the microstructure, operating conditions, and electrode design of polypropylene film. Moreover, we explore insulation modification methods to enhance the resistance of polypropylene films to extreme environments, and introduce material modification methods for polypropylene films based on microstructure regulation, intrinsic doping, interface treatment and multilayer structural design, as well as the development process of metal electrode design methods based on composite film design, safety film design, and asymptotic square resistor design. The paper will provide a reference for the insulation design, production and operation and maintenance of capacitors in service in high-voltage direct current transmission systems.