TiN nanoparticle reinforced AlSi10Mg composite powder was produced by a novel ultrasonic vibration dispersion technique. The TiN/AlSi10Mg composites were fabricated via selective laser melting (SLM). The effects of scanning speed on the microstructure, particle distribution state, and tribological properties of the as-built composites were studied. Experimental results showed a better SLM processibility for the composite powder due to the considerable improvement of laser absorption capacity. The microstructure of as-built composite parts was remarkably refined with a gradually decreased average grain size from 0.388 μm to 0.284 μm by increasing scanning speed compared to that of AlSi10Mg part (∼ 0.579 μm). Nano-sized TiN particles were evenly distributed and well-bonded in the composite matrix while minimized agglomerated TiN particles gathered and grew into large spherical clusters. Because of the in-situ reaction occurred between TiN cluster and AlSi10Mg matrix, novel graded interfacial layers were observed. The mean layer thickness increased from 0.11 μm to 0.38 μm by decreasing the scanning speed from 600 mm/s to 200 mm/s. Taking advantage of the dispersion strengthening, fine grain strengthening, and the graded interfacial layer, a considerably-high microhardness (145 ± 4.9 HV), and enhanced wear performance were achieved.