This paper advances a new method, double phase differences correction method, which aims at correcting the errors of frequency, phase and amplitude of the harmonic signal. The employment of this method involves that two phase differences of two highest spectral lines in the main lob are used to get the correcting value of frequency and then phase and amplitude can be rectified by corresponding formula. It solves the problem that the traditional formula of translation of window center is only for rectangle window. This new formula can correct for the different window by the principle of translation of window center. Simulation shows that the maximum error of frequency of the signal with white noise is less than 1% of frequency resolution. The maximum error of phase is around 1.5º, and the maximum error of amplitude is within 0.01. The average errors in frequency, phase and amplitude are approximately 0.002Hz, 1º and 0.005, respectively.