It is difficult to measure voltage flicker parameter accurately and in real time under a complex power grid environment, a voltage flicker envelope extraction algorithm based on multi-point differential improved analytic energy operator (IAEO) is proposed, which simplified formula for extracting flicker envelope and a novel K-B optimal mutual convolution window function is constructed. Then, the correction formula of flicker amplitude and frequency is derived based on the three-spectral line interpolation of the novel K-B optimized mutual convolution window, and the estimation algorithm of voltage flicker parameter is proposed based on the IAEO and the novel K-B mutual convolution window. Finally, a voltage-flicker-parameter-estimation platform based on virtual instrument is developed. The simulation and experimental results show that the proposed algorithm can effectively measure voltage flicker parameter under single frequency modulation, multi-frequency modulation and fundamental frequency fluctuation. In addition, it can effectively overcome harmonics, interharmonics and noise interference. Compared with the existing estimation algorithm, the flicker envelope extraction is simpler, the measurement result is more accurate, and it is easy to implement embedded.