Using ObjectARX, an integrated CAD/CAM software for steel tubular truss structures has been developed based on AutoCAD platform and Visual studio.Net environment. The design ideas and the application effects are introduced in this paper. Because of different data requirements in different design stages of steel tubular structures, i.e., the whole structure design and the detail design, a wireframe model and a solid model were adopted in the software, respectively. Joint lofting is the key point in manufacturing of complex tubular trusses. To solve this, 3D solid model was constructed by self-defined solid objects, which were designed with inheritance of class AcDb3dSolid in ObjectARX, and Boolean operation was used to realize 3D end lofting of branch pipes. Based on the lofted solid model, the G-codes can be generated automatically. At last, an actual tubular truss structure was designed and lofted by using the software. The proposed software package realizes the integration of CAD/CAM and it can greatly reduce the cost and time of design and fabrication, improve the quality of construction.