To solve the magnetic shielding problem on the polishing inner surface of ferromagnetic pipe fittings with a magnetic grinding method，a magnetic abrasive finishing equipment was developed. Four types of magnetic pole models were analyzed by finite element analysis. The influence of the shape, speed and movement state of the magnetic pole on polishing effect were studied. 40Cr steel was taken as the experimental material for experimental verification, and the surface morphologies before and after processing were observed by using a microscope. The results show that the processing effect is better and the machining efficiency is higher when the magnetic pole is annular, the rotate direction of the pole and workpiece is opposite, and the magnetic pole rotate speed is 2 000 r/min. The surface roughness of the workpiece decreases below 0.25 μm. The micro cracks and potholes on the inner surface of the workpiece are perfectly removed and the quality of the workpiece surface is obviously improved by comparing the surface morphology before and after processing. The magnetic shielding problem can be effectively solved using the poles builtin method and better processing surface can be obtained.