Objective: The flow channel distribution of polylactic acid in four screw extruder with different screw arrangement was studied. Methods: The three-dimensional modeling software Solidworks was used to establish the screw model and the corresponding fluid region model under the arrangement of one-word screw, four-square screw and encircle screw. Numerical simulation was carried out by the simulation software Polyflow. Results: The screw arrangement of monotype and surround type had better pressure building ability and distribution mixing ability than the square arrangement, and the square arrangement had weaker transport ability of polylactic acid. Conclusion: The four-screw extruder with one-line screw arrangement has a good effect on the processing of PLA.