Although metal matrix composites (MMCs) possess high mechanical properties for wide potential applications, there are limited kinds of ex-situ MMCs fabricated via selective laser melting (SLM) until now. In this study, TiN/AISI 420 stainless steel (SS) MMCs samples were fabricated by SLM. Densification behavior, microstructure, hardness and wear performance were investigated with different TiN contents and laser powers. It was found that the addition of TiN has a strong influence on density, which was mainly attributed to its impact on laser absorptivity of powder and wettability of liquid metal. With a higher laser power, the diffusion behavior of TiN became stronger and the densification of composites was improved with a maximum relative density of 98.2%. Both of the distribution and solid-solution of TiN particles were investigated by SEM, XRD and EDS results. The optimized composites achieved a high hardness of HRC 56.7, which is 11.8% higher than that of SLMed pure AISI 420 SS. The wear performance was enhanced due to the improved hardness and TiN reinforcement particle.