To raise calculation speed and analyzing precision of harmonic analysis for special applications

an improved double-spectrum-line interpolation algorithm based on spectral energy centroid method is proposed

and the formulas for calculating the coefficient of arbitrary order cosine window function and parameters correction are deduced. Making use of the values of two discrete spectral lines near each harmonic component

this algorithm can realize the accurate interpolation correction calculation of the signal frequency

amplitude and phase simply and rapidly. Computer simulation results show that the accuracy of the proposed algorithm is comparable to the current polynomial fitting interpolation algorithm

and its calculation is accelerated by more than 10%. The proposed algorithm is suitable for the correction of all harmonic components

including interharmonic component. Experiments prove the effectiveness and practicability of the algorithm.