A flexible auxiliary support device based on magnetorheological fluid is designed to improve the machining accuracy of weakly rigid parts. Use the finite element method to simulate the device’ s magnetic induction intensity through COMSOL software,study the support force provided by it,use engineering mechanics knowledge to perform mechanical analysis on the processed workpiece,theoretical deformation calculation and finite element processing deformation simulation on the processed workpiece,the research is different The influence of the auxiliary supporting device of the magnetorheological fluid on the deformation of the processed workpiece under the state of loading current. Finally,build a test stand,perform milling experiments under the conditions of different milling parameters and magnetorheological auxiliary support devices loading different currents and measure the surface roughness and flatness of the processed workpiece, study the milling parameters and magnetorheological auxiliary support on the workpiece processing surface The impact of quality. The results show that the MRF auxiliary support device can increase the rigidity of weakly rigid workpieces,suppress machining deformation,and improve the machining quality of workpieces.