Abstract: Three aromatic diamines containing fluorine were synthesized. In addition, three kinds of diphenyl ether trifluoride polyimide films were prepared by polycondensation, and the polyimide film was prepared by using 4,4′-diaminodiphenylether(BADE) with 3,3′,4,4′-biphenyltetracarboxylic dianhydride(BPDA) by the same method. The water vapor permeability, water absorption and thermal properties of these four kinds of polyimide film were studied. The results show that water vapor permeability of polymer PI-1(2,2′-BTF-4,4′-BADE+BPDA， BTF：bis(trifluoromethyl)) is 7.70 g/(h·m2), the water absorption is 0.67%, the glass transition temperature is 259.74 ℃，and the temperature of mass loss of 5% is 521.40 ℃, the polymer has good water vapor permeability and low water absorption.

Key words: polyimides, trifluoromethyl, synthesis, water vapor permeability, water uptake