The invention discloses a method for applying a magnetic field to a sputtering coated cathode, which comprises the following steps that: a magnetic field assistant sputtering mode is adopted to perform film coating; a target and a substrate are arranged in an electric field in parallel, the target is positioned on the surface of the cathode so that a plasma zone is formed between the target and the substrate; ions bombard the target to generate sputtering; and the sputtered target atoms or molecules are deposited on the substrate to form a film. The method is characterized in that the back side of the substrate is provided with a magnetic pole facing to a permanent magnet or an electromagnet in the direction of the target, the back side of the target is provided with a ferromagnetic sheetso that the target is positioned in the magnetic field, and the strength of the magnetic field is evenly distributed and the magnetic field is arranged in a direction vertical to the surface of the target. The method can greatly improve the speed of sputtering film coating and the crystallization quality of the film coating, and can etch the target evenly on the whole and improve the utilization rate of the target to between 85 and 90 percent; and simultaneously, the method avoids the corrosion influence of cooling water on the magnet, can achieve sputtering at a high temperature, and is moreadvantageous for improving the sputtering rate of the target.