The work aims to study the influence of magnetic particles finishing on the hole surface quality of SUS304 stainless steel and optimize the process program for grinding the workpiece inner surface by magnetic particle. Firstly, based on single trajectory motion and compound trajectory motion of magnetic pole, the basic principle and motion trajectory of grinding the hole inner surface by magnetic particle were analyzed theoretically. Secondly, the magnetic field strength of the hole inner wall was analyzed for finite element by ANSYS software. Finally, the verification test was conducted by using magnetic particle to grind the inner surface of the hole. The topography and roughness of the hole surface were measured by the ultra depth 3D microscope and the stylus surface roughness meter. When the situation of magnetic pole was single trajectory motion, the process time was 15 min. When the material removal amount of the workpiece was about 662 mg, the surface roughness of the inner surface of the hole was reduced to Ra 0.48 μm from original Ra 2.0 μm. However, when the situation of magnetic pole was compound trajectory motion, the material removal amount of the workpiece was up to 892 mg and the roughness of the hole inner surface was reduced to Ra 0.24 μm from original Ra 2.0 μm. Therefore, as the magnetic pole movement is compound trajectory motion, compared with the traditional single trajectory motion, the grinding efficiency is further increased; the surface topography and surface roughness of the workpiece are obviously improved; and the surface quality of the workpiece after grinding is better than the former.