Abstract: In this paper,a new seam tracking system based on data memory of chip computer is introduced.The system is mainly used for multi-pass and multi-layer welding.In the first welding run,the system not only tracks the weld seam,but also stores the seam tracking data in the chip computer.After the first run,the system tracks the seam depending on the data stored in the chip computer.The accuracy of seam tracking is satisfactory for welding in the both cases.A new kind of two-dimensions tracking mechanical device and a new seam tracking sensor are used in this system.