Use ANSYS/CFX software to analyze the flow channel of a coaxial variable speed single-screw extruder with planetary gears, and compare with the ordinary single screw. Results: compared with the ordinary single screw, the new coaxial variable speed single screw extruder has better pressure building capacity and longer residence time of the material in the screw, which is conducive to better mixing of the material, indicating that the planetary gear is coaxial. The variable speed single screw can locally reduce the material transportation speed, increase the material mixing capacity and the screw pressure building capacity.