Coaxial powder feeding with carrier gas is the key part of laser direct metal deposition (DMD) rapid prototyping system. The convergence of powder flow would greatly affect forming efficiency, precision and performance. Numerical calculation model of flow field was built and simulated in this paper. The results of simulation and analysis had shown that powder flow field was very complex. The flow process could be divided into two parts, converging process and dispersing process. The main influencing factors of convergence included powder feeding rate, carrier gas flow rate, and the distance from nozzle to molten pool. There was a convergent focus where utilization ratio of powder was maximum. So the distance from nozzle to molten pool must be adjusted to equal to convergent focus (1.5cm) during DMD.