In metal forming process by die casting method, nitriding plays an important role in increasing the surface hardness. The influence of shot peening and shot blasting to the modified. H13 tool steel before nitriding process has been studied. Nitriding has been done in a gas vacuum furnace, at temperature of 510°C for 5 hours. Shot peening was conducted by using steel balls with a pressure of 461 kPa. Shot blasting has been done after shot peening using SiC particles. Characterization of the sample surface before and after the variation process is focused on changing the microstructure, micro hardness distribution, depth and composition nitriding layer. It has been found that shot peening prior to nitriding increase the maximum surface hardness to 1196 HV and effective depth of diffusion layer to 72 μm. Meanwhile, the nitriding without any prior surface treatment produces a maximum hardness of HV 1101.4 with effective depth of diffusion layer of 54 μm. Shot peening prior to nitriding produces white layer thickness of 4.1 μm thicker compared to white layer developed in nitriding without shot peening which produces 3.7 μm. While on nitrided material without any preceded surface treatment did not reveal any white surface layer.