Objective: To explore the differences in runner performance of screw groups with different differential ratios, and to clarify the effects of differential speed on the extrusion performance of polylactic acid materials. Methods: Four groups of differential twin screw groups were established by Solidworks software, meshing and finite element numerical simulation were carried out by Fluent software, the calculation results were analyzed by CFD-post software, and the contours and discounted plots of various characterization parameters were combined, and they were verified by experiments. Results: Under the condition that the inlet and outlet pressures were 0.2 MPa and 0.5 MPa, and the reference speed of a single head was 30 r/min, the screws with a differential ratio of 1∶2 and 1∶3 had their own advantages and disadvantages under different properties, and the screws with a difference ratio of 1∶2 for output and pressure in the barrel had an advantage. In terms of mixing capacity, a screw with a differential ratio of 1∶3 had an advantage. Conclusion: Compared with the traditional twin-screw extruder, the differential twin-screw extruder has a positive impact on the extrusion performance of polylactic acid materials, and can be used as a new polylactic acid production equipment.