This system is based on the TMS320 f28335 chip. The welding voltage and current values are acquired in the whole welding process by the AD function,and are handled by some specific tracking algorithms. After then the PWM signal is output to control and track the motor action. At the same time,this system exchanges data with the PLC and teaching device by the SCI function. Finally,the arc length tracking and effective control are realized in the conditions of the high welding speed or high impulse frequency. The developed tracker can track and control the arc lengths of various welding without adding a specified extension module. The actual welding proves that the effects of the arc length tracking and control are good,and the expected welding target is achieved.