Abstract: The present study introduces a path planning algorithm of the two-robot coordinate system in welding task of complex curve seam. Furthermore, a leader-follower scheme has been proposed, according to the molten pool of each points on whole seam are nearly vertical or horizontal,which guarantee one robot catching work piece to adjust seam lying in the flat position under pose constraint and the other tracking and welding. In this research, the two-robot coordinate system and coordinate mathematical model has been established for constrained pose. Moreover, the paper study on path planning in two-robot coordinate which saddle-shape weld seam as study objects. Finally, test on path planning was done in order to prove the theory results, while the test results and analysis show that the two-robot coordinate system can realize continuous welding for complex curve seam.