To solve the problems of the high power radio frequency (RF) slab CO2 laser surface oxidation by copper electrode discharge and RF discharge electronic sputtering which leads to rough electrode surface, an uniform glow discharge and serious optical loss and so on. The magnetron sputtering coating technology is used for laser electrode surface plating Al, and then anodic oxidation into Al2O3 waveguide dielectric film, based on the effect of anomalous dispersion and high temperature resistant ability of Al2O3 waveguide dielectric film. The influence of magnetron sputtering process on the film structure is analyzed; the reflectivity of the electrode coating to CO2 laser is measured and the discharge experiment is tested. The results show that when the sputtering power is 250 W, the compact film structure can be obtained; Al2O3 thin films with thickness of 6 μm , have the highest reflectance peak of 75% to CO2 waveguide laser wavelength of 10.6 μm ; The laser output power at a 30% duty cycle is 700 W, in the duty cycle of 60% reaches 1300 W after electrode coating.