A cutting device for eradicating shaping and deformation of rails is characterized in that an internal combustion plasma cutting medium frequency power supply is an internal combustion medium frequency generator with only a rotor and a stator; the generator can output three groups of independent medium frequency current; and the three groups of independent medium frequency current satisfies the electrical characteristic needed by plasma arc cutting and power control of the automatic walking and cutting trolleys of the rails. The three groups of independent medium frequency current not only has wide voltage adaptation range but also can be clustered in the same cable with a working gas pipe and an arcing current circuit, thus being simpler and more convenient for site operation. The cutting device is simplified, has smaller volume, high reliability and high efficiency and is simple to operate. Through the electronic rectification technology, the cutting device changes the electrical and mechanical conversion mode, improves the electrical response speed, reduces the energy conversion loss, ensures 100A stable cutting current, thoroughly solves the problems of maximum conversion from power output power to cutting power and stability and conforms to the high-precision and high-efficiency requirement for eradicating shaping and deformation of the rails.