In the spaceflight delivery system,some small size thin-walled parts have high requirements for the weld quality. Manual TIG welding is usually used for these parts. The weld quality is unstable and is easily affected by human factors. Welding robot has the characteristics of low fault rate and stable welding quality. An automatic TIG welding robot workstation is designed. This workstation can realize automatic welding and adjustable welding parameters,and has the arc length tracking function and can automatically adjust the height of the welding gun to ensure the stability of the weld. The overall design of the machine and the realization of the automatic welding function are briefly introduced. The realization of the arc length tracking function is described in detail. The workstation performance is verified through welding experiments of straight weld,circumferential weld and square weld.