The corner white Mura issue of product “A” produced in line 6 generation was systematically studied. Firstly， the physical analysis was carried out for the defects， and then the data simulation analysis was carried out by using the binary logistic regression method of Minitab software. Finally， the defects were analyzed and improved through different process test conditions. The experimental results showed that the sealant in defect region was sheltered by metal wiring， and the shielding proportion was an important factor affecting the corner white dot. Further analysis by TOF-SIMS showed that defect region had higher content of sealant （acrylic acid， bisphenol A）. Thus， the sealant was sheltered by metal wiring， resulting in incomplete curing of the sealant in this region， leading to the precipitation of the sealant component into the liquid crystal， which then affected the normal deflection of the liquid crystal， resulting in white dot in the corner at last. By adjusting the corner of the sealant painting， it could effectively reduce the defect rate. This experiment effectively improved the corner white dot， laid a firm foundation for the smooth mass production of product “A”， and reduced the loss of the company.