Abstract: The concepts of arc welding robot with redundant degree of freedom and its autonomous path planning were presented,the significance of inducing redundancy in welding production was discussed,controlling variable method was adopted as an approach to optimize redundant degree of freedom for arc welding robot,considering welding orientation parameters,a new method of incorporating multiple criteria was presented,function of welding orientation parameters,function of position constraints and function of motion stability were defined.As to space complicated weld seam,after autonomous path planning with this method,the changes of joint angles were smooth and far away from the limitations,the motion of the robot was stable,and at the same time it could meet the requirement of weld quality,the problem of autonomous path planning of arc welding robot with redundant degree of freedom was effectively solved and its results were satisfying.