Abstract: Laser conditioning is a process w here the damage threshold of the coating is increased or the damage created is minimized so that it does not grow upon further irradiation. It is feasible that the damage threshold be improved safely and the power density sustain by the laser system be stepped up by studying the mechanism and technology of laser conditioning systematically. From the changes of several sol-gel films and PVD films during laser conditioning, some damages occurred. The damages are correlated to defects of the film itself and the beam parameters. It is proved that laser conditioning can eliminate film defects step to step.