The project aims to develop an automatic inspection system for the etching transistor on the TFT-LCD panel and conduct the automatic inspection on line and application in the related measurement. To develop and integrate the related automatic optical inspection system, we use an auto-focusing sub-system and the isolator in the system to contain the vibration caused by the movement of machine and environment, increase the system stability, ensure the quality through entire image process and guarantee all acquired images to be distinct. The image inspection process uses the pattern match methodology to seek and find the thin-film transistor and build the images database to execute the image match, then decide the kinds of the target etching transistors image, and calculate the center of this electrode pattern image, the result can be transmitted to servo control system of the equipment and moves image capture hardware to the center position of electrode pattern image, it carries out the relevant follow-up measurement of line width, line distance of the transistor pattern image.