The invention provides a method for eliminating residual magnetism of a transformer core. According to the method for eliminating residual magnetism of the transformer core, the residual magnetism of the transformer core is eliminated by virtue of a low-frequency low-voltage alternating-current demagnetization method, wherein the adopted alternating current is heavy current. The method provided by the invention can be used for well improving the onsite transformer demagnetization effect, saving the test time and manpower cost, and furthermore avoiding economic losses brought by long-time power failure caused by unfinished tests.