Abstract: Aiming at the multi-layer and multi-pass welding process of thick plate with large groove, a multi-layer and multi-channel welding path planning algorithm was proposed. Firstly, the geometric dimensions of the weld cross-section were obtained by robot vision system, and then the number of weld layer and the pass number of each layer are planned according to the groove shape, and finally the starting and ending positions of multi-layer and multi-pass welding were determined. In the welding process, in order to avoid the deformation of workpiece caused by repeated multi-pass welding, symmetrical welding method was introduced. RobotStudio software offline programming was used to verify the accuracy of the algorithm, and the welding quality and efficiency of the robot were verified by welding test. The results show that the method avoids tedious process of the manual teaching, improves the welding efficiency, and the groove filling effect and weld formation are good after welding.