Abstract: In order to solve the weld seam tracking problem in the pulse TIG welding process of some thin stainless steel workpiece with complicated curved surface,a high precision and rapidly responsing speed seam tracking method based on visual sensor has been developed in this paper.According to the process characteristics of pulse TIG welding,special wavelength filter and reasonable exposure schedule have been selected,the clear and amplified welding image (from which weld seam,weld pool and tungsten electrode could be identified directly) could be acquired with industrial CCD camera.Then,an image processing algorithm has been programmed with Visual C language.With this algorithm,the central line of weld seam could be detected rapidly and precisely,the direction and distance which the tungsten electrode deviates from the central line of weld seam could be calculated out,the step motor has been driven to adjust the position of welding torch.Therefore,the precise and real time weld seam tracking has been realized.Experimental result shows that,processing time for single image is less than 120 ms,the seam tracking could be carried out if the angle between welding direction and weld seam is no more than 30°.Finally,the thin stainless steel workpiece with complicated curved surface has been successfully welded using this method.