The forming mechanism of the multi-component polymer melt is always the difficult problem in the study on the composite fiber, due to the difference of the material properties. The study simulated the flow of PET/PA6 composite melt on the influence law for the velocity distribution and the micro hole＇s structure on the influence law for extrusion swelling based on the theory of the rheology and the spinning process and the structure of the spinning components by Polyflow. In addition by comparison with the previous experiments about extrusion swelling, the results show that the value of the swell ratio decreases rapidly at low values of length/ diameter and then levels off as length/diameter is increased further, whereas increases with the die exit angle increasing. The veincity distribution of the composite melt and the micro hole＇s structure have a significant influence on the extrusion swelling, which has very good guidance function for studying the forming mechanism of the composite melt and preparation of the high performance fiber.
