The barrier properties of epoxy resin and its bonding with other materials is improved by changing the performance of resin-encapsulated power electronic capacitor materials. At the same time

the improvement of the structural design of the capacitor reduces penetration of water vapor and solves the problem of heat and humidity resistance of the capacitor in the field of wind energy photovoltaic and the like. The test verification of the modified capacitor is performed by the damp heat durability test and the long-term damp heat endurance test. The improved capacitors passing the long-term damp heat durability test can assure safe and reliable operation of cylindrical power electric capacitor at severe environment.