Works based on the theory of engineering electromagnetic fields and high current busbar, study on the GIS (Gas Insulate Substation, referred to as GIS) in the steady-state model of the equivalent shell, and calculate the model parameters. Normal operation, circulation value of the shell and busbar load current is essentially the same order of magnitude. They also have a huge circulation loss and influent transmission capacity of the system. The phenomenon of heat loss also occurs at the same time of circulation loss generating. When circulation above a certain value, heat loss over heat capacity of the shell. It will lead to local heat and accelerate aging of insulation. Therefore, it is great significance for the value of the steady circulation to establish an accurate equivalent model of GIS shell. By referring to the existing home and abroad on the aspects of research about the equivalent model of the GIS shell, use the high-current busbar theory to establish an accurate equivalent model of GIS shell.