For the double taper screw of the screw extruder used for propellant extrusion molding, the mutual shear and extrusion action of the charge is greatly improved when a certain process is adopted. Using ANSYS finite element analysis software, by simulating the flow distribution, stress distribution and the fluid-solid coupling of the charge in the extrusion process, the strength analysis of the existing screw was carried out to check whether it is suitable for the new technology. The maximum pressure difference in the flow passage was taken as the optimization objective, and the screw strength was taken as the constraint condition. By changing the structural parameters of the screw, the extrusion efficiency of the screw extruder was improved. The results show that the influence of wedge angle on the maximum pressure difference of the flow passage is more than screw width.By the orthogonal test, the best parameter combination is the wedge angle are both 24° and the width of the screw is 1.5 mm, the pressure difference in the extrusion passage reaches the minimum under this parameter combination.