<p>Laser powder bed fusion (LPBF) is a promising technique for the fabrication of nanoparticle-reinforced titanium matrix composites. Controlling and minimizing particle agglomeration is critical but very challenging in the development of nanoparticle-reinforced titanium matrix composites using LPBF as the formation of particle agglomeration can degrade the mechanical properties of the resulting composites, especially the ductility. In this study, we investigated the effect of molten pool fluid dynamics on the nanoparticle dispersion uniformity during the LPBF process of 10 wt% TiC/Ti6Al4V composite by numerical simulation. Since the existing methods to track the migration of reinforcement particles, like multiphase model or discrete element method (DEM), were faced with challenges, a user-defined scalar transport model in which the reinforcement particles were simplified as a scalar function was utilized to track the migration of TiC nano-particles and implement the coupling of particle dispersion and molten fluid dynamics. The simulation outcomes indicated that the molten fluid with nano-particles was subject to the evaporation recoil pressure and Marangoni effect, forming distinctive C-shaped patterns in the longitudinal section and TiC-rich stripes in the transverse cross section. The increase of laser heat input and the decrease of scanning velocity favored the uniformity of particle dispersion. The overlapping effect of the melt track during multi-track scanning exhibited an essential influence on particle dispersion, with an appropriate overlap rate of about 50%, while successive layer fusion had no significant effect on overall uniformity of particle dispersion.</p>