The gas insulation switchgear, which is a device for protecting a power system, cannot be supported by the insulation gas itself in a charge unit stored in a metal container. Therefore, molding technology is required to manufacture a gas insulation switch spacer. The APG method injection molding simulation was performed by applying the variables obtained through the physical properties of an epoxy composite used for manufacturing an insulating spacer to a moldflow software. After varying the temperature conditions of heater in the simulation, the thermal characteristics and the degree of hardening of the spacer were analyzed, based on which the optimum process conditions are presented.