Abstract: This paper presents a new kinematics modeling of the intelligent arc welding in the real time trajectory tracking.The new method is called welded line tangent method which forms a kinematics model for the robot operating in the bent degree based on the judgment of the tacking system.With the method,the kinematics models for the four wheel robot and instantaneous of mobile machine was set up.Experimental results show that control characters and accuracy are satisfactory and this controller can meet the requirements of the welding application.