In order to improve the damage threshold of semiconductor laser facet film and increase the laser output power, the causes of the catastrophic optical mirror damage in the laser are discussed. The highest field intensity in the high-reflective (HR) film is moved out of the interface in view of the damage principle. The reflectance and electric field distribution are simulated with film thickness changing continuously by using optical transmission matrix to get the optimized high reflective film, and the film damage is reduced at the interface by the optimized film. LaB6 with improved higher plasma density is adopted as in situ plasma source, and the cleaning parameter of ion source is optimized. In the earlier period of preparing film, facet deoxidation is made with ion pre-cleaning in vacuum environment, and the film is fabricated with ion-assisted electron beam evaporation, and the stability of the film is tested under high temperature and high humidity environment. The laser output power is raised from 4.5 W to 7.02 W, operating current is raised from 5 A to 8 A in the case of the quasi-continuous operation with the optimized film and cleaning method.