Eccentricity is strictly limited for the high-accuracy spheric rotor(e.g.used in gyroscope).A new method named difference-velocity corrosion is proposed based on principle analysis of eccentricity correction.Since corrosion reaction happens between rotor and some corrosive,by controlling corroding time,the points on the surface of rotor will have different paths,so that eccentricity correction can be achieved.The control law of difference-velocity corrosion is deduced and verified by test.The test results show that a rotor with eccentricity of several microns can be corrected to 0.5 μm by once-through operation.