The work aims to improve the processing efficiency of 30CrMnSi high-strength structural steel surface by magnetic abrasive finishing technology and solve the problems of weak magnetic field intensity and low utilization rate of magnetic energy in permanent magnet magnetic abrasive finishing. Firstly, the material removal mechanism of 30CrMnSi ferromagnetic workpiece was analyzed, and the importance of magnetic induction intensity B to the material removal of the workpiece was discussed. Then, based on Halbach Array, the magnetic field was designed, and the size of permanent magnet unit and magnetic field layout scheme were determined by theoretical calculation and simulation analysis. At last, the single factor finishing experiment of 30CrMnSi plate was carried out by self-made adhesive magnetic abrasive. According to the magnetic field calculation and simulation results, the optimal magnetic field arrangement scheme was determined for the Halbach Array permanent magnet Array with two cycles, and the ideal magnetic field gradient and optimal magnetic field distribution were obtained. The processing experiment of 30CrMnSi plate showed that the roughness decreased (%ΔRa) increased with the increase of magnetic pole speed and abrasive mesh number. When the mass ratio of ferromagnetic phase to abrasive grain (hereinafter referred to as the two-phase mass ratio) in magnetic abrasive was 3∶1, the magnetic pole speed was 500 r/min and the number of abrasive mesh was 240 and the best processing effect was obtained. The surface with Ra=0.129 micron was obtained, and the maximum reduction percentage of roughness was 90.74%. Designing the permanent magnet field with Halbach Array can increase the magnetic field strength of the processing area and improve the processing efficiency of the 30CrMnSi high-strength structural steel surface.