Abstract: Diamond-like carbon(DLC) films were deposited by un-balanced magnetron sputtering(UBMS) technology and a comparison of their damage morphologies with and without external electric field was then made. With the applied electric field, a large amount of filiform films appeared and the damaged area decreased as well. Thus the external electric field influences the damage morphology of DLC films. Under the influence of the electric field, the photoelectrons excited by laser in the films will perform a speedy movement, which indirectly reduces the energy density in some parts of the laser-irradiated area and slows down the graphitizing process of the films. As a result, the films are more difficult to be damaged by laser.