The invention discloses a method for improving measurement accuracy of a generator PMU device. With introduction of injection voltage elimination enabling, an injection voltage amplitude upper limit,an amplitude gain and an amplitude offset into a calculation program, a zero-sequence voltage component injected into a generator terminal voltage is eliminated and then PMU measurement calculation isperformed, so that pseudo-oscillation generated by the low-frequency voltage component injected by an injected stator grounding protection device in PMU device measurement data is eliminated and thePMU device measurement data still can reflect the oscillation or fault state of the system truly even when the true oscillation or fault occurs in the system. Meanwhile, because of an elimination algorithm based on an instantaneous sampling value of a time section, no extra time delay of the PMU device measurement data is caused, so that the measurement accuracy of the generator PMU device is improved, the operating state of the generator set is reflected truly, and the reliable and accurate data source is provided for the power grid dispatch monitoring system.