Considering the four factors such as groove depth,width,lead and slot numbers of the screw barrel,numerical simulation and orthogonal analysis method were used to investigate the influence of the four factors on the performance of the single screw extruder with helically grooved barrel. An optimum structure of the barrel was obtained. The results showed that,the performance of extrusion and mixing was the best when the groove depth of barrel of 0. 6 mm,width of 4. 5 mm,lead of 20 mm and slot number of 3 were used.