High temperature oxidation resistant coatings were prepared by nitriding and siliconizing the surface of Mo-W alloys with different tungsten content by in-situ reaction method. The influence of W content on the morphology and microstructure of coating was analyzed by Scanning Electron Microscope and X ray diffraction. The oxidation resistance properties were also evaluated. In addition, the mechanism of anti-oxidant was researched. The results indicate that the amount of silicon seepage on the coating surface decreases as W content in Mo-W alloy increasing, which reveals that the increase of W content can slow down the outward diffusion of Si element effectively. Furthermore, the high temperature oxidation experiment at 1600℃ proves that the Mo-30%W surface coating has the best oxidation resistance, and the oxidation resistance time is up to 327 h. As a result, the increase of tungsten content improves the oxidation resistance of the coating to a certain extent.