The thesis work is to show that the use of SLM (Additive Manufacturing) compared with the traditional process to make injection molds will have advantages in design, especially in waterways.  This thesis work gives seven different versions of design applied to the SLM method to analyze and compare them in Solidworks® and Moldflow® to figure out what design is suitable for the SLM method. Through analysis of different versions, the finding of this thesis work is that the conformal waterway of design and lighter but stead structure in the SLM method causes the SLM molds' cooling performance to be almost 15% better than the conventional way and shorten the production time by 18% per product. Based on the advantages of the SLM method in cooling system design and structure optimization, the company can use the SLM method in the production process to improve economic and environmental benefits.