Understanding the mechanism of dielectric breakdown is important for improving the breakdown field of a polymer. In this work, dielectric barrier discharge (DBD) treatment was applied to one surface of P(VDF-CTFE) (vinylidene fluoride-chlorotrifluoroethylene) film, and the dielectric properties of the film were studied. When the treated surface was connected to the high potential side of the power source for the breakdown test, the breakdown field of the treated film was significantly reduced compared to that of the pristine film. Based on the characterization results for the surface chemistry and morphology, it was proposed that the phenomenon was caused by the combined effects of hole injection from the metal electrode and the damage of polymer chains near the surface of the polymer film after the DBD treatment process.