Inorganic nanohybrid polyimide (PI) has wide applications in electric and electronics for its outstanding insulating, mechanical and heat-resistance properties. Al2O3/PI nanohybrid films of 100CR (Dupont), with excellent corona-resistance, were characterized by synchrotron radiation small angle X-ray scattering (SAXS) and transmission electric microscopy (TEM). The results show that the inorganic particles are 4-7 nm in size. The interface between nanoparticles and matrix is sharp. Fractal dimension of the film is 2.48.