In this paper，the stress characteristics of charged particles at the interface of type I and type Ⅱ in DC-link capacitors are analyzed from point view of the motion path of the charged particles in series dielectric structure.The electric field force of the charged particles at the gas-film interface is analyzed and calculated. It is explained that why the space charge problem is not prominent in oil-immersed capacitor but prominent in dry metallized film capacitor is because of the design field strength. It is suggested that improving the element heat setting process and using oil impregnation process can improve the space charge accumulation effect of medium structure. The influence of space charge injection on dielectric breakdown voltage is verified by the breakdown voltage data analysis of polypropylene film in accelerated aging test capacitor. By measuring the space charge of the metallized polypropylene films after accelerated aging test，the existence of space charge injection in DC-link capacitor is verified.It is suggested to strengthen the study of space charge in DC-link capacitor film and its influence，find out the boundary and improve the performance as well as operation reliability of capacitor.