The development of the traditional digital flicker meter is realized by converting the analog filter of each link into digital filter according to the flicker measurement principle provided by IEC. However, the effectiveness of the digital filter is limited by the sampling frequency and the transformation selection. To achieve accurate extraction of the voltage flicker envelope signal, the analytical mode decomposition is used to improve the filter link in the square detection method. A new KN mutual convolution window is proposed. The correction algorithm, which is based on the KN mutual convolution window and the threespectral line interpolation, is realized. The flicker parameter detection method based on improved square detection method and new KN mutual convolution window is proposed in this study. The flicker parameter detection platform based on virtual instrument is developed. Simulation experimental results show that the proposed algorithm can effectively realize the accurate detection of flicker parameters in the cases of single frequency modulation, multifrequency modulation, power grid frequency deviation, containing superposition harmonic interference and noise interference. This method is easy to realize and its accuracy is higher than the traditional detection methods.