For the vibration problem of desulfurization mixer caused by fluid,the conventional three-type mixer was used as the research object,the modal analysis method based on unidirectional fluid-solid coupling was used to make the modal analysis of the mixer under the action of fluid.By analyzing the stress and deformation of the mixer under the action of fluid,the harmonic response analysis of the maximum equivalent stress position of mixer was carried out.The results show that the maximum flow velocity in the iron water tank is located in the regional fluid near the mixing head,and the maximum velocity is 1.2 m/s;the minimum flow velocity is located in the fluid near the tank wall,the minimum velocity is 0.1 m/s;under the fluid-solid coupling,the maximum equivalent pressure appears at the mixing shaft and mixing blade connection,the maximum equivalent pressure is 2 299.6 Pa;when the excitation frequency is the first and third order nature frequency,the vibration response of the mixing head reaches peaks respectively;when the excitation frequency of the agitator is 260 Hz,the peak displacements of y and z directions reach 0.001 6 mm and 0.000 3 mm respectively;when the excitation frequency of the agitator is 1 800 Hz,the peaks displacements of y and z direction reach 0.006 3 mm and 0.002 2 mm respectively.