The blue laser has significant meaning in the application fields of biological engineering, laser screen, laser medical technology, investigation, communication and many fields of science. The resonant cavity is an important component of laser, how to make it work effectively turns to be a major subject. Aimed at the operating requirements of blue laser cavity surface film, based on Nd:YVO4, Ta2O5、SiO2 are chosen as coating materials. The films are prepared by vacuum coating equipment and double ion beam assist deposition. Through technics feedback analysis to the test result by several simulation experiments, the electric field distribution is optimized, which can decrease the damage of thin- film from laser. The reason of extremum method cumulative error is described, as well as reasons of control differences of short wavelength range and long wavelength range. By analysising optical thickness caused by refractive index, adjust the tool factor. The filter coating with well- optical performance, low- absorb, and steady- chemical properties is prepared, which satisfy the operating requirements of blue laser.