When used under the non-synchronized sampling and non-integral period truncation conditions, the electrical harmonic analysis by Fast Fourier Transform (FFT) has large error due to spectral leakage and picket fence effect. In order to reduce the error, the paper analyzes the spectral characteristics of four-term fifth derivative Nuttall window, an approach for harmonic analysis based on four-term fifth derivative Nuttall window and triple-spectrum-line interpolation FFT is proposed, the explicit rectification formulas of frequency, amplitude and phase are obtained by using polynomial curve fitting. Simulation results for 21 order harmonics indicate that the algorithm has a better analysis precision compared to Blackman window, Blackman-Harris window interpolated FFT and the double-spectrum-line interpolation, effectively restrains the influences of fundamental frequency fluctuation as well. Experimental result of voltage signal actual collected further demonstrates the validity of approach presented.%非同步采样和非整数周期截断时，由于频率泄露和栅栏效应，快速傅里叶变换（FFT）的电力系统谐波分析误差较大。为减小该误差，本文分析了四项五阶Nuttall窗的频谱特性，提出了基于四项五阶Nuttall窗三峰谱线插值FFT的谐波分析算法，运用多项式拟合推导出频率、幅值、相位的修正公式。含21次谐波信号仿真结果表明，相比于常见的Blackman窗、Blackman-Harris窗插值FFT和双峰谱线插值，本文算法精度更高，同时本文算法能有效克服基波频率波动对谐波分析的影响。对实际采集到的电压信号的实验研究进一步证明了该方法的正确性。
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