Abstract: It is difficult to use traditional grinding methods to remove internal surface microcracks of the space bending pipe. Device based on six degrees of freedom manipulator for magnetic abrasive finishing can grind internal surface of the space bending pipe. In order to improve the efficiency of magnetic abrasive finishing, grinding and polishing mathematical model was established and increasing grinding pressure was effective. Therefore, proposed using the spherical magnet as assisted polishing tool in the grinding medium to improve the grinding pressure for the bending pipe inner surface. The Ansoft Maxwell software analysis indicates the magnetic flux density increased by applying the spherical magnet in the processing area. This means an increase of grinding pressure. By performing grinding of TB8 alloys bending pipe, it can be seen that grinding efficiency was increased by 40% after adding spherical magnet, surface roughness was as low as 0.09 μm. In addition, the microcracks on inner surface of the TB8 alloys bending pipe were removed. It is feasible to use spherical magnet auxiliary grinding for surface finish of inner surface of bending pipe.