Abstract: Screw is the key component of extruder and must have very higher performance reliability because of high temperature and high pressure workingconditions. Screw parameters directly affect the quality and productivity of the extruded products, therefore, the optimized design of screw parameters is of great significance. By means of modern design method, screw model was establishedand inputted into ANSYS using Pro/E. Three-dimensional stress analysis was carried out for screws with four different radii and cross-sections of the taper screw including rectangle sections without, with single and double round angle transition for strengthening, and trapeziform section. The analysis results show that the strengths of the screws with double round-angle transitional rectanglesection and trapeziform section are the biggest, that with single round-angle transitional rectangle section is the second, and that without round-angle transition is the worst because of serious stress concentration. The research resultsprovide basis for further study on screw design optimization and stimulation ofextruding experiments.