The flow of melt poly ethylene in double -screw extruder , “ —” -shaped tri -screw ex truder , triangular tri -screw extruder and four -screw extruder was analyzed by means of ANSYS/FLOTRAN .The special study focused on the central area of reactor' s flow path of triang ulartri -screw extruder and four -screw extruder .Ex trusion characteristic of four types of reactors was compared.The results show that a large velocity gradient emerges in the intermeshing region of the screw reactors, which is helpful to mix materials sufficiently .The four reactors have different numbers of intermeshing regions .Double -screw reactor , “ —” - shaped tri-screw extruder , triang ular tri -screw extruder and four -screw extruder have one, two , three , and four intermeshing regions respectively .With the increase of the number of intermeshing regions, the mixing ability of materials is enhanced gradually . Triang ulartri-screw extruder and four -screw extruder have special structure, that is, central region.Materials in the central region form circumfluence , which promotes the mixing effect and prolongs the mixing time of materials in the central region .Through calculation , the materials cannot be hold up in the central area .For double -screw extruder , “ —” -shaped tri -screw ex truder , triangular tri -screw extruder and four -screw extruder , flow rate , back flow rate , coefficient of back flow rate and average rate of shear are incremental gradually .It is verified in theory that the multiple -screw extruders have good material transpor tation and mixed ability .Multiple -screw extruder is fitter for polymer processing .