Abstract: The internal flow field and structure field of internal mixer were analyzed under three different conditions usinga calculation method based on oneway and twoway fluidsolid coupling.The equivalent stress in the maximum stress position and maximum displacement position of structure field were achieved, and the transient shear rate and fluctuation of maximum displacement were also obtained.The results indicated that the shear rate of flow field could be determined by the geometrical shape of rotor.The main frequency of shear rate fluctuation was one times of the rotor edge frequency.The results from the twoway coupling calculation were higher than those from the oneway coupling one.The stress of rotor edge and the distorted distribution were consistent with the two coupling calculation, and the main frequency of the fluctuation is mainly determined by the low frequency generated by rotor edge meshing.The rotor geometry was considered as a main influence factor of maximum stress wave.The stress wave had little effect on the rotation position frequency in the maximum stress point, but it had great effect on the maximum displacement position.