Abstract: According to the welding particularity on the junctions of intersecting pipe, the 4 degrees of freedom suspended welding robot was developed and mechanical structure of the body was introduced. Based on the relation of the joints, the kinematics modeling was established with the method of D-H (Denavit-Hartenberg). To overcome the size error and processing error and welding distortion, the welding track was taught in order to ensure welding quality, and then theory track was amended by the linear interpolation. According to the kinematics modeling, the simulation was carried out with SemMechanic. The results of experiments show that the welding quality meet the requirements actually.