Abstract: This paper focuses on the dual-robot welding coordination of complex curve seams that one robot grasps the workpiece while the other holds the torch, then the two robots work on the same workpiece coordinately.The dual-robot coordination system is established at the beginning, after that, the non master/slave scheme is chosen for the kinematics trajectory planning.The non master/slave scheme sets the position and poses of the point on the workpiece, and calculates the end effecter trajectories of both robots through the constrained matrixes respectively.Downhand welding is employed in the kinematics trajectory planning that can guarantee the torch and the weld in good contact condition all the time during the welding process.Moreover, a Solidworks-SimMechanics platform is established for motion simulation, and an example of curved steel pipe welding is conducted.The results indicate that the established platform is accurate and effective for the task planning and analysis welding coordination of two robots.The output trajectories of both the joint displacements and end effectors are the same as predefined ones.