Spectral leakage and fence effect influenced the analytical accuracy of signal, which were caused in asynchronous sampling, it was hard to verify the PMU, so an interpolation FFT algorithm was proposed, and derived the formulas of magnitude, phase, frequency of signal. The results got a high accuracy through verification of experiments and simulation, and the verification method of PMU based on high accuracy data efficiently achieved the comparison and analysis. Finally according to the algorithm and verification method, high precision calibrator of PMU was developed and achieve the high precision verification, it makes the efficient run of power grid.