The 4WS rotor is a new type of internal mixer rotor, and the ratio of long and short edge length is one of the important geometrical structure design parameters. The flow fields in 4WS rotor internal mixer with ratio of long and short edge length, 2∶1, 3∶1 and 4∶1, were simulated by using the software POLYFLOW. Through particle tracing technology, the macroscopic mixing state of the three internal mixers was visualized and tracked.Using the flow field data, the typical evaluation parameters of dispersive mixing and distributed mixing were calculated, and the mixing efficiency of the fluids in three different rotor internal mixers was compared and analyzed, and the effect of ratio of long and short edge length on mixing characteristics of 4WS rotor mixer was explored. The results show that, compared with the 4WS rotor internal mixer with a length ratio of 3∶1 and 2∶1, the dispersing and distributed mixing ability of 4∶1 type rotor have been greatly improved.