According to the .DXF file of the two-dimension graphics designed under the software of AutoCAD R14,the paper presents a method of designing C++ procedure in the VC++6.0 Studio to realize to transfer data in the .DXF file of boiler's tubeplate and work out the maximum hypothetical equivalent circle among all kinds of drawing-supporting component.The method is efficient to confirm the most unsubstan-tial district for the tubeplate,it provides the gists of design for the optimum design of industrial boiler's ...