Flicker is an important index of TFT-LCD image quality evaluation. Based on the mechanism of ΔVp and flicker, the influence of Vcom on flicker is studied, and the experiment results show that Vcom has a significant impact on flicker. With the increase of flicker gray level, the optimum flicker tends to decrease gradually and its corresponding Vcom for TN mode products decreases gradually, while ADS mode products increases gradually. Secondly, the article studied The impact of VGH and VGLon flicker is stadied, the results indicate that VGH and VGL have important impact on flicker. When flicker gray level is invariable, the VGH increase will not affect the optimal flicker, but the corresponding Vcom decreases gradually. While the VGL increase the optimal flicker decreases gradually, but the corresponding Vcom increases gradually. A quantitative analysis method is proposed for predicting flicker scales of different gray level and proved that it can be used to predict the flicker scale of different gray level, because the calculated flicker is consistent with measurement flicker value by FMA test method under VESA standard, and the linear correlation coefficients are above 0.95 for both TN mode and ADS mode products. These studies provide analytical methods and solutions for improving TFT-LCD flicker problem.