Abstract: In allusion to problems of big error and slow operation speed of traditional harmonic detection methods in power network, the paper proposed a detection method based on FFT algorithm, introduced fixed-point operation of DSP chip and specific implementation of harmonic detection method based on FFT algorithm, and did simulation analysis. The method realizes FFT algorithm using high-speed fixed-point DSP chip TMS320F2812, normalized the data to Q15 format to calculate, and used windowed interpolation FFT algorithm for harmonic analysis to reduce impact of spectral leakage on detecting result. The method realizes harmonics detecting of power network and ensures detection speed and accuracy.