Traditional magnetic abrasive polishing process is only suitable for processing one side of the workpiece, but it cannot polish double-surface at the same time. To overcome the shortcomings of current methods, this paper presented a new magnetic polishing process based on annular magnetic field, which can polish both sides of the workpiece simultaneously. Electromagnet with annular magnetic field was designed, and then finite element simulation analysis was carried on. In order to further explore the effect of current intensity, the clearance between the magnetic pole and the workpiece, the spindle speed and polishing time on surface roughness, double-surface polishing experiments were carried out on the material of stainless steel. It was concluded that the surface roughness Ra decreased with the increase of polishing time, working gap and spindle speed. Orthogonal test scheme was designed to obtain the reasonable process parameters and experimental verification was made. Finally, a good surface roughness on both sides was obtained. The experiment has proved that the method can polish both sides of the workpiece surface at the same time, and the surface roughness Ra of two surfaces decreases from the original 0.2 μm to Ra (S) = 0.094μm and Ra (N) = 0.068μm respectively.