Abstract: An efficient bypass arc welding method was presented.By employing common CCD camera with composite filter glass,the clear image of welding pool was captured under the condition of continuous high current.With digital graphic processing technique,images were processed in real time by IMAQ module of Labview.The best morphological processing approach was obtained by comparing the width of molten pool extracted in various image processing methods.The width of molten pool can be measured and the data can be saved automatically.It laid a foundation for the realization of quality control in double-electrode MIG welding.