Direct energy deposition (DED) is a promising additive manufacturing process for fabricating metal matrix composite (MMC) components. Using reinforcing particles as nucleation sites, the DED process can produce fine-grained MMC parts with enhanced tensile properties. However, coexistance of interactive phenomena (e.g., Marangoni convection, recoil pressure, and multiple reflection) with extreme short period of their presence in the melt pool hinders the control of particle dispersion, which is crucial for obtaining superior mechanical properties with equiaxed grain structure. To resolve this problem, the numerical model incorporating thermo-fluid dynamics is established to predict flows in the melt pool. Also, based on the constructed simulation results and Lagrangian discrete phase model (DPM), migration patterns of particles are investigated. The obtained results showed that recoil pressure and Marangoni convection forces had a significant role in the movement of particles. The present study better explains the dispersion mechanism of supplementary particles in the melt pool.