The flanges used in connection of pipes, pipe fittings or equipment will produce defects such as microcracks and folds on the internal surface during processing, which will lead to a decrease in service life. It is difficult to finish the internal surface of flange tube with traditional polishing process,but it can be realized by magnetic abrasive machining process. The grinding test platform was refitted from the spindle of the XK7136C CNC milling machine.In this grinding test platform,the magnetic pole spindle drives the magnetic pole with side slot to rotate under the given cutting path of numerical control program,so as to realize the purpose of finishing the internal surface of the flange tube with magnetic abrasive. The principle of machining flange tube surface and the force of magnetic abrasive were analyzed. The results show that the surface quality of the internal surface of the bend of flange parts is obviously improved after finishing, and the surface roughness is reduced from 3.46 μm to 1.18 μm，which is verified that magnetic grinding has a good effect on the internal surface finishing of the flange pipe.