Abstract: Firstly,this paper demonstrates the working principle and technical requirements of a teaching-playback Tungsten Pole Argon Arc Welding Robot with four degrees of freedom which designed by us. Secondly,the structure of computer system,kinematic equations,trajectory motion plan and trajectory interpolation are given. It briefly introduces the design of a numerical servo system. One of the specialities of thissystem is that it uses a special motor control IC. The key technique of Tungsten Pole Argon Arc WeldingRobOt is anti-interference of high frequency and high vortage. Some methods to resolve this problem are proposed at the end of this paper.