The invention provides a preparation method of a molybdenum disilicide series oxygen diffusion coefficient verifying diaphragm, and method used for calculating film oxygen diffusion coefficient. The preparation method comprises following steps: SiO2 base solution preparation, oxidation corrosion resistant doped solution preparation, mixing of a working mother liquor B into a working mother liquor A at different ratios, silicon chip washing, silicon chip doping film preparation, and baking of generated amorphous film in a high temperature tubular furnace. The preparation method is capable of prolonging the service life of MoSi2 heating elements, increasing using temperature, and realizing accurate verifying of oxygen diffusion coefficient, so that the industrial value is high, and the application prospect is promising; and at the same time, the method used for calculating film oxygen diffusion coefficient is simple, convenient, and accurate, and possesses significant meaning in study on high temperature corrosion mechanisms.