LCD TVs are developing in the direction of large size and ultra-thinness. The glass substrate is subject to the influence of gravity caused by the increase in size and the problem of backlight heating, which in turn affects the optical characteristics of large-size LCD TVs and causes display defects. Therefore,this paper explains the large size from the perspective of the change of light transmittance of liquid crystal panel by using the liquid crystal panel mechanical test and establishing 65-inch LCD TVs model and optical simulation model, using the combination of finite element simulation and TechWiz LCD optical simulation. The LCD TVs displays the defect mechanism. Finally, when the tilt angle is less than 0.5 ° and the operating temperature is lower than 40℃,the liquid crystal panel can effectively reduce the display defects of large-size LCD TVs.