Based on FLUENT software, a three-dimensional simulation of polymer melt’s flow pattern in the three-screw extruder(TTSE) was carried out, with the flow pattern and mixing pattern of polymer melt within the screw analyzed. Polymer melt’s shear rate distribution map, the mixing index distribution map in three-screw extruder were obtained as well as polymer’s residence time distribution(RTD) within the runner and were compared and analyzed with the mixing performance in twin-screw extruder(TSE). Results show that the dispersive mixing capability and distribution mixing capability of three-screw extruder were stronger than those of the twin-screw extruder, while the residence time of materials was longer because of the presence of the central circulation zone in the three-screw extruder. Therefore the three-screw extruder would have good prospects in practical production and application in the future.