Abstract: A set of apparatus for measuring magneto-optical polarizing Kerr hysteresis loop was designed and built up. By adjusting laser power, it can change the temperature of tested points of thin film samples irradiated by focusing light. The distribution of temperature within TbFeCo magneto-optical film irra-diated by laser is simulated by calculating. The relationship between film coercive force and irradiatinglaser power is obtained. According to it, the Curie temperature and compensation temperature of filmsare determined. It presents an effective way to study the variation of magneto-optical characteristics offilms under different temperatures and the magnetic coupling properties of multiplayer magneto-opticalfilms.