4WS, 4WH and 6WI rotors were regarded as the object of study. According to the theory of fluidstructure interaction, fluid solid coupled finite element analysis models of internal mixer were established, and the coupled equations of liquid material and solid rotor inside internal mixer were solved. Under the circumstance of constant power, the influence rules of the stress and deformation of rotor under rotate speed were researched. It was found that the stress and deformation were leaded by the coupling of torque and fluid load , and the torque was the main factor resulting in stress and deformation. With the increase of rotate speed, the mixing effect of materials was significantly improved. The torque caused by rotate speed and the change of fluid load leaded to the change of rotor clearance. Rotor clearance had significant influence on the mixing effect. 6WI rotor had better mixing effect. The research results provided theoretical reference for the reasonable design and performance prediction of rotor in internal mixer.