Traditional polyimide film’s color is yellow because of inter-and intra-molecular charge transfer complex (CTC). Based on molecular structure design, a new diamine named 3,5-di (2-trifluoromethyl-4-amino)-1-tri. fluoromethyl-tuluene is designed and synthesized. The new colorless polyimide film is prepared from the polymeriza.tion between the diamine and the dianhydride 6FDA through one-step method. Through infrared absorption spectra (FTIR), UV-vis transmittance and thermal performance (DSC/TGA) testing on the polyimide film, experimental re.sults that the polyimide film has a high degree of imization, high visible transmittance, maximum transmittance of88.9% and high glass transition temperature, which Tg is 275.48℃, high thermal decomposition temperature Td5% is 550℃, and Td10% is 582℃.