Abstract: Based on the theory of static magnetic field, the surface magnetic field on the high-resolution multi-pole magnetic drum for a magnetic rotary encoder was analyzed. The visual curves of the surface magnetic field distribution were obtained by numerical calculation and plotting. A good AMR magnetic head for the magnetic rotary encoder was designed. The results of theoretical analysis and practical test were contrasted. The results are accorded in the output signal's shape and amplitude of the AMR magnetic head and its multi-frequency characteristic.