Free-form surfaces have widespread applications in the fields of integrated circuit, and automobile sectors because of the typical geometric characteristics. Surface finishing of free-form surfaces is a critical process to fulfill target quality. In present study, a magnetorheological shear thickening finishing (MSTF) method is proposed for Sine surface finishing based on the designed finishing tool and the developed MSTF media. The MSTF utilizes a flexible finishing tool, integrating a slotted cylindrical permanent magnetic pole with radial magnetization, is fabricated to dominate rheological properties of finishing media to guarantee the finishing force. To obtain sufficiently large magnetic flux density and magnetic field gradients in the finishing zone, finite element analysis (FEA) is used to obtain the optimal dimensions and structure of the finishing tool. The principle of the method is illustrated and mathematical model of material removal is established. Finishing experiments were conducted on Sine surface fabricated by SUS304 based on the developed MSTF media and the established platform. The effects of finishing parameters on surface roughness are evaluated quantitatively. The results substantiate that the material was uniformly re-moved over the entire Sine surface and the developed method is capable for Si-ne finishing with a more than 87% improvement in surface roughness. The method in the paper shows signs of future success in finishing free-form surfaces in a wide range of industrial applications.