Objective To investigate the effects of the flight edge angle at the end face of the screw rotor in a counter-rotating twin-screw extruder on the extrusion performance of polylactic acid (PLA).Methods Experimental screws with flight edge angles of 70° and 80° were compared with a standard screw (90° flight edge angle) as the control. Mesh generation of the screw elements was conducted using Gambit software, followed by numerical simulations in Polyflow to compare the differences in pressure fields and shear rates within the flow channels of the three screws. The residence time and distribution of tracer particles were obtained via the Polystat post-processing statistical module, and corresponding curves were plotted to evaluate the extrusion capacity and distributive mixing characteristics of the three screw designs.Results At the same screw rotation speed, reducing the flight edge angle weakened the local high-pressure effect in the flow channel. Among the three screws, the 70° flight edge angle presented the optimal shearing performance, followed by the standard screw. Screws with smaller flight edge angles exhibited stronger material conveying capacity, higher screw area utilization, and superior distributive mixing performance.Conclusion The flight edge angle at the end face of the extruder screw rotor significantly regulates the flow field characteristics, conveying capacity, and mixing performance during PLA extrusion. Appropriately reducing the flight edge angle can simultaneously lower local high pressure in the flow channel and enhance material conveying efficiency and distributive mixing. Among the tested designs, the screw with a 70° flight edge angle demonstrates the best comprehensive extrusion performance.