Abstract: The seam tracking system is introduced,where the rota-ting arc sensor drived with hollow axle motor is used,the teaching arcwelding robot is used as controlling object.Based upon the signal processing method for the real state on the rotating arc sensor,the methods of seam recognition for space position such as flat position,horizontal position and vertical position are studied.A fuzzy control approach is utilized for designing the welding seam tracking system,which is successfully applied to seam tracking for above positions and will inerease greatly the au-tomatization of teaching welding robot.