Abstract: The flow field and rotor of 6I rotor internal mixer were analyzed by a transient analysis method, and the velocity vector diagram, shear rate cloud map, velocity and pressure curves at specific points were obtained at different time. The flow lines at different positions were also analyzed. The results indicated that the mixing effect of flow field in the middle mixing zone was not only influenced by the extrusion of the top of edge, but also promoted by the propelling flow from the front of edge. The discharge of the long edges resulted in bending deformation of edge, which greatly affects the stress distribution in the rotor edge. The axis position of rotor and the stress distribution at the root were greatly influenced by the shape of the top of rotor. Although the axial discharge of the long and short edges was disadvantageous to the formation of the drag and drop flow, the discharge generated a positive effect on the overall mixing flow. Most of spiral upwelling was produced at the middle edge, which could gather a large number of fluids and guide the axial flow at any positions.