Novel polyimide with better thermostability, lower dielectric constant and constant loss were synthesized by fluorinated modification and molecular structural design and predicted as coatings with highly electromagnetic wave permeability. 4-(4-aminophenoxy)-3-fluoroaniline (APFA) was obtained by 2-fluoro-4-nitrophenol and 4-nitrochlorobenzene, then the formed 2-fluoro-4-nitro-1-(4-nitrophenoxy)benzene(FNNB) was transferred by catalytic reduction with hydrazine hydrate and catalyst of Pd/C. The asymmetric fluorinated was synthesized with 6FDA in DMAc solution by imidization of polyamic acid. Asymmetric polyimide exhibited excellent thermal stability with the decomposition temperature and the glass transition temperature of 502.50 and 251.60 ℃. The residual weight (Rw) at 700 ℃ was 49.86％. AFM images of polyimide film showed that the grain sizes were in narrow ranges with evenly surface and mean roughness of 9.024 nm. The UV-Vis absorption edge was at 357 nm and the transparency at 450 nm was higher than 80％. The dielectric constant was 3.65 at 1 MHz and 2.38 at 10 MHz, and the maximum dielectric loss was 0.010 7.