In this study, simulation studies were conducted to develop insert injection molds to improve the mass production of terminal assemblies. For the main part of the automobile door latch, charging, holding pressure and deformation analysis were performed according to the gate position of the injection process. As a result of injection molding analysis of the terminal assembly, the flow pattern was uniformly made while maintaining a constant balance of the filling of the product, and the pressure distribution at the time of filling was confirmed. When the analysis results are applied to the mold fabrication in the improved structural method, the transfer lines of the molten resin are controlled by the dam of the 1st injection molding, so that the transmission line is not short-circuited or deformed, and the watertightness, corrosion resistance, and good surface We believe the injection will be possible.