By modifying the lighting fixture of the LCD box and adding a logic operation small box and optical probe， the transmittance of the LCD box was tested. The polarizer was attached to white glass， the polarizer carrier was slotted， and the driving voltage of the LCD box was measured and programmed to match and test the transmittance of the LCD box and module products； Through experiments， it was found that the transmission rate of the optimized and renovated lighting fixture test LCD box was consistent with the fluctuation trend of the module transmission rate， which could meet the needs of LCD box transmission rate screening. Products with high transmission rate fluctuations were intercepted in advance， effectively avoiding the waste of back-end module materials.