Abstract: The spherical powder for 3D printing prepared by gas atomization has fine particle size and high sphericity, which is suitable for large-scale industrial production. Atomizing nozzle is the core component of the gas atomization process. Its structural parameters, especially the melt tip taper angle of the delivery tube, have a great impact on the gas atomization results. Meanwhile, changing the taper angle of the melt tip is more effective and economical than changing the atomization process parameters such as gas pressure and temperature. In this paper, the computational fluid dynamics (CFD) method was used to simulate the internal flow field variation in the spray chamber with different melt tip taper angles. The commercial CFD software FLUENT is used to calculate and visualize the complex multiphase flow process in the closed spray chamber with high temperature and high pressure. The results show that the direction of air flow can be changed by changing the melt tip taper angle (16°, 22°, 28°, 34°, 40°, and 46°). With the change of the taper angle, the stagnation point position, the stagnation pressure and the suction pressure in the single-phase flow field show regular characteristics. The influence of various factors in the single phase flow field on the melt breaking effect was analyzed. Secondly, the Volume of Fluid (VOF) model was used to simulate the primary atomization process. The results show that the mass median diameter (MMD) of the primary atomization also varies with the change of the melt tip taper angle. The droplet size distribution after primary atomization can be controlled by changing the melt tip taper angle. In the case studied, the minimum MMD was 304 μm when the melt tip taper angle was 34°.