Abstract: The structural optimization in Laval nozzle is analyzed by the numerical simulation based on CFD-DEM coupling method, and the effect of structure parameters of Laval nozzle on the outlet pressure of the nozzle is discussed through the orthogonal test with 4 factors 3 levels. The results show that the injector based on the stack effect is conducive to draw the powder into the injector; when the throat length becomes longer, the diameter of the throat becomes narrower, the cone angle of the contraction tube or the diffusion tube becomes smaller, the outlet pressure of Laval nozzle will increase. The outlet pressure of the Laval nozzle is most affected by its throat length, followed by the tube diameter, again the cone angle of the contraction tube, and finally the cone angle of the diffusion tube. By adding the primary Laval nozzle and increasing the length of the throat, the smoothness of the feeding can be improved, and the powder can be transported over longer distances.