<p>Thin-walled parts are more likely to vibrate and deform under milling process because of weak stiffness, which results in unsatisfactory machining accuracy. To solve this issue, a deformation suppression method for thin-walled parts during milling process based on shear thickening fluid (STF) and preferred machining path was proposed in this paper. Two types of STFs silicon dioxide-polyethylene glycol 200 (SiO₂-PEG200) and cornstarch-water were adopted for auxiliary support of thin-walled parts during machining process. A deformation prediction model was established from the perspective of energy based on Lagrange’s equation considering the rheological and mechanical properties of the STFs, and the prediction error for the maximum deformation point was controlled within 8.5% for the demonstrated highly concentrated STF systems. Milling experiments on thin-walled parts with different STFs were performed to verify the theoretical model. Experimental results demonstrated that STFs could enhance the deformation resistance of thin-walled parts by providing effective support during machining. Furthermore, the machined surface roughness is significantly decreased, leading to an overall improvement in surface quality. The influence of machining path on the deformation of thin-walled parts was analyzed. Experiment results indicated that combining 60% cornstarch-water STF and bilateral symmetric layered milling, the smallest machining deformation was obtained, which was reduced by 84.1% compared to the unidirectional layered milling condition without STF.</p>