A new technology and implementation method for the development of theoretical line loss calculation software of graphical high-voltage power grid using VBA using Microsoft Visio2003 graphics software as the platform are proposed and studied. The mathematical model and algorithm of theoretical line loss calculation of high-voltage power network are plotted. The general graphical modeling method of power system based on the drawn electrical wiring diagram, and the automatic identification of power grid topology are studied. Developed a practical graphical high-voltage power grid theoretical line loss calculation software running in Visio2003. The development practice shows that Visio’s secondary development technology provides an effective way for the development of graphical high-voltage power network theoretical line loss calculation and other power system calculation software