Die casting offers low cost in mass manufacturing of complex shaped components with acceptable casting results. Further, the selection of die-casting parameters and the addition of reinforcing elements can also improve the mechanical properties of aluminum. In this study, the Al-Si matrix strengthened using High Pressure Die Casting method with reinforce agent from snail shell powder (calcium carbonate). Further, this study also explores the mechanical properties and microstructure of the product produced through experiment and optimization. The optimization was adopted to identify the optimum parameter using the Taguchi method. The results suggested that the reinforcing agent from the snail shell powder has the CaO and Ca(OH)2 phases, with a crystallite size of 106.59nm. The morphology of the reinforce agent showed the presence of agglomeration and interconnected structures with average particle size of 0.4 μm. The functional group of the reinforcing agent showed the O-H band during the water absorption by CaO, along with asymmetric C – O with vibration from the carbonate group and Ca – O bound. The highest hardness number was identified from T8, with 403.2 HRB and with 0.15% reinforce agents, 750oC temperature injection, and 50MPa pressure. Meanwhile, the best tensile strength was found from the T9 sample, with 109,95MPa and 0.15% reinforce agents, 800oC temperature injection, and 60MPa pressure. Microstructure of die casting sample with snail shell powder reinforcing agent showed the presence of Al, Si, dendrite, and Al4Ca phases. The multiple respones on the three factors indicated that the reinforcing agent presented the most significant effects toward the tensile strength and hardness, followed by pressure and temperature injection. Meanwhile, the Taguchi method and ANOVA results showed the optimal parameter die casting was obtained from a combination of 0.15 wt% reinforce agent, 800oC injection temperature, and 50MPa pressure.