Fast Fourier transform (FFT) is the most widely used method in power harmonic analysis recently. Although when used in asynchronous sampling, it is easy to generate the spectrum leakage and the fence effect. In order to reduce the influence of asynchronous sampling on FFT, the five-term Rife-Vincent (I) window with low side-lobe peak level and fast descent rate are analyzed and applied to FFT algorithm, and quadruple –spectrum-line interpolation FFT harmonic detection algorithm based on five-term Rife-Vincent window is proposed. Based on the polynomial function fitting, a simple and practical interpolation correction formula of four spectral lines is derived, which makes the calculation process easier. The results show that compared with Hanning window, Nuttall window and four-term Rife-Vincent (I) window interpolation FFT, five-term Rife-Vincent (I) window has the higher accuracy under the same conditions. And it’s amplitude relative error≤6.52434E-5%, phase relative error≤7.75054E-3%.