4,4'-diamino-2,2'-bistrifluoromethylbiphenyl (TFMB), 4,4'-(hexafluoroisopropene) diacetic anhydride (6FDA) and 3,3',4 4'-biphenyltetracarboxylic dianhydride (BPDA) were used as the reactive monomer, a series of fluorinated copolyimide films were prepared by changing the proportion and feeding method of non -fluorinated monomer BPDA. The properties of the films were characterized and analyzed. The results show that both the feeding method and the proportion of BPDA in the dianhydride monomer can affect the properties of the films. The prepared fluorinated copolyimide films are soluble in the aprotic polar solvent at room temperature, and the film have a high light transmittance in the visible light range. As the content of non-fluorinated dianhydride monomer BPDA increased the optical properties of the film decrease slightly, while the thermal properties and mechanical tensile properties were improved. When the proportion of non-fluorinated dianhydride monomer is 68.97%, the transmittance of the prepared copolyimide film still maintains in 96.01% at 500 nm; When the non-fluorinated dianhydride monomer account for 35.71% of the dianhydride monomer, the thermal decomposition temperature at a weight loss of 10% of the prepared copolyimide film is 595.23℃, correspondingly the tensile strength is 100.98 MPa. The change of feeding mode of BPDA have different effect on the optical properties, mechanical properties and mechanical tensile properties of the copolyimide film.