The Finite Element Method was used to study the flow field of different screw combination sections of single?screw extruder. The Polyflow software was used to calculate the pressure field, shear rate field, velocity vector, mixing index and other parameters of the flow field of ordinary screw, ordinary screw and pineapple head combined screw, ordinary screw and pin combined screw. The post?processing results were compared and analysed.The results show that the ordinary threaded screw can provide a greater axial velocity for the fluid; although the pineapple head screw has greater resistance, the more oblique section design can provide better axial and circumferential velocity for the fluid; the barrier effect of the screw causes a part of the fluid to flow back. The three new types of screws can effectively stretch and shear the fluid while providing a good linear velocity for the fluid to make its dispersion and mixing more uniform. According to the analysis of the curve results, the mixing effect of pin?screw is the best.