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Metallized film capacitors (MFCs) have been widely commercialized, and the insulation failure has become an important issue under high electric field. However, due to the self-healing characteristic, the MFCs offer a notable advantage in electrical insulation. This work aims to optimize the process of manufacturing in MFC in self-healing performance and explore the development process of self-healing in metallized film from experiment to theoretical model. In self-healing experience, the thickness of dielectric layer is negatively correlated with the performance of self-healing and winding tension in manufacturing is positive instead. The self-healing in metallized films have an incomplete but fierce combustion producing gas product like C2H6/CO and a large amount of H2. On the other hand, the self-healing process did not produce polar fragments/groups in dielectric layer, as indicated by Fourier transform infrared spectroscopy (FTIR). The SEM scan suggests a strong correlation between self-healing and carbonized area on the surface of dielectric layer. A small amount of metallic elements was found to remain in the self-healing area, with no metallic oxide particles. However, a large amount of graphite is composited in the clearing area along with a certain amount of element O. The simulation result of theoretical model built on plasma theory shows a depth of $0.28~\mu \text{m}$ in carbon area, accounting for 5% of the 5.8- $\mu \text{m}$ thickness of dielectric layer. In addition, the radius of carbonized area in dielectric exceeds the evaporated area in metallized layer by 1.5 times.