The invention discloses a method for preparing an amorphous carbon coating on the surface of a medical stainless steel knife saw. The method includes the following steps: preprocessing, ion cleaning, electric arc discharging, and carbon ion depositing. An amorphous tetrahedral carbon film prepared by the method has the characteristics of high bonding strength, excellent biological property and good corrosion resisting performance; after a salt fog test for 48 hours, no corrosion spot is incurred on the amorphous tetrahedral carbon film. After the surfaces of resin, stainless steel and the like are coated, the corrosion and abrasion resisting properties are greatly enhanced, the anti-ageing function is obvious, and the service life is greatly prolonged. After the above surfaces are coated, material bacteria cannot be adhered, so as to solve the cleaning problem of an oral cavity after artificial teeth are installed, thereby being beneficial for the health of the oral cavity. After the above surfaces are coated, the growth of cells on the surfaces is in good condition, and the cell density is higher; moreover, the thicker the film, the better the growth of the cells. The coating stainless steel knife saw prepared by the method in the invention has the following characteristics: the rigidity of the knife saw can be up to more than 85GPa, the content of an SP3 bond structure of a coating is equal to or higher than 85%, the friction coefficient is within 0.08 to 0.15, and the binding force between the film and a basal body is within 35 to 45N.