Objective In order to relieve the urgent demand of market of polyimide, polyamic acid and polyimide films were prepared, and the effects of different parameters on the intrinsic viscosity of polyamic acid were discussed. Methods Polyamic acid solution (PAA) and polyimide films were prepared by two-step method and thermal imidization, respectively. The parameters of the monomer ratio, the reaction temperature, the reaction time and the water content in system were optimized by experiments, and the intrinsic viscosity and the microstructure of polyamic acid and polyimide films were characterized by ublelohds viscometer, Fourier transform infrared spectroscopy（FTIR） and X-ray diffraction （XRD） . Results The optimized parameters were: the monomer ratio BTDA/ODA of 1.02, the reaction temperature of 20 ℃, the reaction time of 4 h, the water content in system of 0%. Under this condition, polyamic acid solution with high intrinsic viscosity was obtained, and polyimide films with intact structure were prepared by thermal imidization. Conclusion The polyimide films prepared were homogeneous and transparent, with integrated structure.