A method for improving corrosion resistance of a high abundance rare earth permanent magnet by high temperature oxidation is provided. By the oxidation at 700˜1000° C., a rare earth oxide film grows in-situ on the surface, which can greatly improve the corrosion resistance of the high abundance rare earth permanent magnet. The method makes full use of phase formation rule and diffusion kinetic behavior of high abundance rare earth elements La/Ce/Y, which is different from other rare earth elements Nd/Pr/Dy/Tb. The method grows the rare earth oxide film in situ with strong adhesion to the matrix, which can not only greatly improve the corrosion resistance of the magnet, but also improve the magnetic and mechanical properties. The method has advantages of green environmental protection, long service life and simple process, and can be popularized and applied in large quantities.