Abstract: The topological structure of welding mobile ro-bot was analyzed.The topological structure of welding mobile ro-bot is mainly differential drive robot body and rapid adjustment cross sliders with several freedoms.According to the position of welding torch,namely,at the front,side,the axial line of the robot,or the welding torch can be rotated around the mid-point of axial line of driving wheels,the topological structures can be further sub-divided into four types.The simulation results show that the different topology has different kinematic behavior and suitability for seam tracking of different welding types.In parti-cular,the topology that the welding torch located in the axial line of driving wheel is simple,flexible and easy to approach the narrow welding space,it is an ideal choice to track the complex curved line and wide-angle broken line.The studied results pro-vide an analysis basis for the different application of welding mobile robot.