In laser direct metal manufacturing process by coaxial powder feeding, the interaction between powder and forming sample will occur forming jet blocked, and easily lead to rebound in metal powder nozzle clogging and pollution lens, which affects the forming process. Therefore, the powder optimizes the nozzle cone angle of the powder cavity, and the laser cavity is imported the protection gas in the axial direction. Under the function of the three-route gas (middle route gas, carrying powder gas, outer layer protection gas), the influence rule of the above parameters on the powder gathering characteristics is simulated by FLUENT, and then combined with orthogonal test, to establish the theoretical basis for the laser direct metal forming. The results show that the blocked jet, In the blocked jet, the nozzle cone angle focal length the greater is the larger the powder together, optimized parameters chooses 75°. It is guaranteed that the three-route gas outlet pressure is balanced and the powder gathering concentration is biggest, and optimized parameter: middle route gas m=0.3m3/h, carrying powder gas q=0.24 m3/h, outer layer protection gas Q=0.1m3/h.