Abstract: The modeling could contact the solid model of the robot with its modeling data, which made these solids identified by the off-line programming system, in the off-line programming sy stem of the arc welding robot by the second development.The model was the base of the whole off-line programming system.In the surrounding of UGNX4.0, the equipment modeling of arc welding robot consists of three key module including part motion module, assemble modeling module and motion module.In the three of module, the part module is the base of them, and then the assemble modeling module and the motion module were taken.The models of the arc welding robot and positioner were successfully founded, which grounded the second development in the ground of UG and by using VC++ as the tool of the second development.