Abstract: This article analyzes sensing method of arc welding pool. With respect to spray transfer pool, compound filters system composed of 405 nm or 1065 nm narrow-band filer are used, and respective pool images are obtained. Compared with each other, more clear pool image can be found through filter set composed of 1064 nm narrow-band. Characters of spray transfer pool are studied. Based on these characters,through computer image processing such as Gauss filter, gray stretch, border detection etc., a clear and sequential pool contour is acquired.