The invention discloses a high-precision harmonic analysis method of sampling data synchronization, which is suitable for the field of power grid harmonic analysis and can realize accuracy computation of frequency, amplitude and phase of a power grid signal. The technical scheme of the invention is as follows: 1, a quadratic polynomial reverse interpolation method for accurately determining a fundamental wave period ensures that the computing precision of the fundamental wave period is improved by 2 orders of magnitude (reaching 1.51*10<-7> percent); and 2, a radial primary function interpolation method used for synchronizing nonsynchronously-sampled data ensures that synchronization data errors subjected to radial primary function interpolation are improved by 3-4 orders of magnitude (reaching 1.1*10<-9> percent). The invention has the advantage that the computing precision of harmonic parameters (amplitude and phase) on the basis of synchronization data is improved by 4-5 orders of magnitude.