This paper presents a magnetic coupling for a large-sized mixer, which is separated by a vessel wall. In order to improve the transmission-torque, the magnetic material attached magnetic-flux concentrated surface permanent magnet (MCSPM) arrangement is applied to the magnetic coupling and the construction is optimized. The results show that the MCSPM arrangement is very effective to improve the air-gap magnetic flux density and the transmission torque even quantity of very few permanent magnets.