Aromatic polyimide was prepared by vapor deposition polymerization(VDP), reacting a diamine monomer with a dianhydride monomer. Evaporation characteristics of monomers were investigated and several polyimide films with low dielectric constant were prepared by the VDP method, focusing on chemical structures as the means to raise the heat resistant temperature. The rod-like (3,3'-4,4'-biphenyl tetracarboxylic dianhydride(BPDA)/o-tolidine(OTD)) polyimide films have dielectric constant (epsilon) = 2.9, and thermal stability above 500 degrees C. The semi-rod-like (pyromelliticdianhydride(PMDA)/2,2-bis[4-(4-aminophenoxy)phenyl] propane(BAPP)) polyimide films have epsilon = 2.7, and thermal stability above 400 degrees C. The polyimide films have other good electric properties such as low leakage current density, high dielectric breakdown strength and no-ageing dielectric constant.