A melting and solidification mathematical model under stationary or moving laser beams at various laser powers P and scan speeds V is established to simulate the selective laser melting of copper-tungsten powder system. The transient temperature and velocity field as well as the forces acting on tungsten particles are obtained, and the metallurgy behavior in the laser-powder interaction zone is analyzed. The results indicate that when the laser power P ranges from 600 W to 900 W, the value of velocity field angle θ decreases from 50° to 0°, implying the enhancement of heat transfer from laser center to edge of molten pool. Under the condition of a stationary laser beam, P≥800 W, or for a moving laser beam, linear energy density η=16 kJ/m, there exists the second flow around the tungsten particles, leading to the formation of pressure acting on the tungsten particle induced by the pressure difference. As the included angle of attractive force and pressure is acute angle, tungsten particles tend to form small-scaled rim structure and the rearrangement rate is limited, accordingly tending to form segregation structure. Otherwise, tungsten particles tend to form large-scaled rim structure and the rearrangement is efficient, contributing to the formation of homogeneously distributed structure.