Abstract: This paper analyzes the insulation resistance characteristics of metallized film capacitor under high electric field, and shows that the insulation resistance is the comprehensive result of the dielectric leakage and self-healing under high electric field. An insulation resistance testing method is presented for the high metallized film capacitors under high electric field. The test results indicate that, for operating electric field ranging from 300 to 400 V/m, the insulation resistance decreases rapidly with the electric field increasing, but because of the self-healing, the decrease gradually slows down. The insulation resistance follows similar rules within the operating temperature range of 20 to 50 ℃.In addition, the dielectric leakage under high operating temperature and electric field reduces the capacitor voltage significantly, affecting the energy storage efficiency of the capacitors and pulsed power systems.