Voltage fluctuation and flicker caused by grid-connected wind power generation and the application of large fluctuating loads have become a problem that can"t be ignored in smart grid. The envelope of the voltage flicker is extracted by the energy operator, and the flicker envelope is modified by the FFT spectrum of the six cosine window and three-spectral line interpolation in this paper. A voltage flicker parameter detection method based on energy operator and six cosine window three-line interpolation is proposed, and the detection and analysis of flicker parameters are realized accordingly. The simulation experiment proves that the detection algorithm of this paper maintains high detection accuracy when it contains single amplitude modulation wave modulation, multi-frequency amplitude modulation wave modulation, grid fundamental frequency variation, harmonics, interharmonics and noise interference. The algorithm is simple to implement and strong in anti-interference, and can realize real-time online detection of voltage flicker parameters effectively.