TFT White Color Uniformity (WCU) and SiNx film thickness of each layer were tested based on the same test points and the correlation between them is analyzed. It is found that TFT WCU has a great correlation with GI and PVX2 layers rather than PVX1 layer with the thinnest THK and largest n value. On this basis, an improvement scheme to reduce the center value of GI Remain THK(to avoid the residue of GL layer) and PVX2 THK (to improve the uniformity in panel)at the same time is proposed, which can reduces the mean value of TFT WCU by about 0.000 7. After improvement, the maximum value can be decreased from 0.007 0 to 0.005 2 to satisfy the specification(maximum value ≤ 0.005 5). The effect of improvement is obvious.