The backlight foreign matters can undermine the display quality because they cause white spots on the thin-film transistor liquid crystal display screen. Research on the failure mechanism for such white spots shows that the issue is caused by the foreign matters between backlight films. Due to the variance in temperature and humidity or the influence of external force, such matters will expand or contract to the extent of off-specification, thus pressing or even scratching the film materials. As a result, the backlight module’s light path will be damaged, and the screen will present abnormal bright spots. To solve this problem, the key factors causing such matters in the process are screened out by fishbone diagram and cause-effect matrix. Then the countermeasures are developed by Six Sigma for the continuous improvement of standardization. Finally, the significance and effectiveness of such countermeasures are verified by double-ratio hypothesis testing and environmental testing. Experimental results show that the failure rate caused by backlight white spots decreases from 0.3% to 0.04% after the improvement. In addition, the fault feedback ratio can reach the standard continuously, indicating significant improvement.