The invention discloses a thin film capacitor. A capacitor core comprises a composite film, a double-side metalized ZnAl film, and a metal spraying layer. The composite film and the double-side metalized ZnAl film are arranged in a staggered manner. The double-side metalized ZnAl film is evaporated on two side surfaces of the composite film. Moreover, the outer end of the capacitor core is provided with the metal spraying layer. The composite layer is made of the following raw materials: polyethylene glycol terephthalate, 2-chloro-3-nitrotoluene, silicon-contained polycarbonate resin, conductive black, barium titanate, chemical resistant modifier, acetone, heat resistant agent, flame retardant synergist, cerous nitrate, chloro-series fire retardant, antioxygen, 3-cyano-5-fluborophenylboronic acid, nanocrystal cellulose, silver oxide, lactate cobalt, ammonium tetrathiomolybdate, sodium borohydride and inorganic nanoparticles. Through employing the self-made composite thin film, the capacitor is small in size, is light in weight, and is good in self-healing performance. The capacitor employs the technology of ZnAl edge thickening evaporation, is excellent in electrical performance, and is high in reliability.