Aiming at the problems of screw extruding 3D printing nozzle, such as easy blockage and insufficient extrusion force. In this study, a screw structure suitable for desktop metal 3D printing forming is designed, which can realize the miniaturization transformation from industrial level to desktop level. By establishing the three-dimensional solid model of the screw device and combining with the formula, the core structural parameters of the screw are analyzed. For the index of screw extrusion flow, the Taguchi Design Of Experiment (DOE) method was used to establish the L16(44) orthogonal test table for the optimal combination of factors. Simulation results show that the width and depth of the screw groove have the greatest effect on the extrusion flow; The optimal screw structure parameters: effective screw length L=60mm, slot width W=6mm, slot depth H=2mm and screw lead M=8mm. The velocity field, pressure field and shear stress field are better by the optimal combination of factors design.