Polyimide has always been the first choice for high performance polymer materials, with excellent thermal stability and good mechanical properties. In this study, we can made a polyimide film with strength and high porosity by cross-linking reaction which in low content (20 wt%) polyimide. The film is formed during the molding process by NIPS (Nonsolvent Induced Phase Separation) method, porous structural can increase the insulating function.And we find out that the polyimide film which forming under 5°C water has the best insulation effect even in different testing temperatures (80°C、100°C、120°C、140°C).