This paper explores the application of the cooling techniques and Moldex3D software for simulation of cooling system in the injection molding process. The effect of cooling systems as the most important factors in optimization of plastic injection molding. Optimization of cooling system plays a significant role in the quality, efficiency, and the cost effective manufacturing. The importance of shape, type, and the location of cooling channels using the Moldex3D software and good results are achieved. Using numerical simulation tools or combination of analytical and numerical simulation approach is one of the intelligent choices applied to modern mold cooling design. Keywords - Injection Molding, Moldex3D Software, Optimization of Cooling Channels.