Abstract: Aiming at the problem of machining accuracy caused by the difficulty of clamping thin-walled parts in aerospace industry and other fields, a flexible fixture based on the magnetorheological fluid (MRF) was designed. Combined with the curing characteristics of MRF to improve the strength of the auxiliary support of the weak stiffness structure, and the key factors such as the magnetic field strength and position affecting the workpiece stiffness was considered. Maxwell was used for magnetic field simulation, and the experimental verification was carried out. The magnetic field strength, shear stress and milling force were tested, and the relationship among them was studied. It is found that the greater magnetic field strength, the greater shear stress and the smaller milling force. Compared with other traditional fixtures, the results are indicated that MRF fixture can improve the clamping performance. The acceleration value with MRF is 0.29g, which is 82.4% lower than that without MRF, and the vibration during machining is significantly reduced. Compared with machining without MRF, the concentricity value is reduced by 38.5% with MRF. The related achievements provide support for machining and clamping technology of thin-walled parts in aerospace field.