To　improve　the　poor　braking　performance　of　the　traditional　eddy　current　retarder,　a　novel　retarder　is　developed　by　coupling　the　eddy　current　effect　and　the　magnetorheological　effect,　which　has　large　torque　at　low　speed　and　stable　torque　at　high　speed.　To　meet　the　constant　speed　requirement　in　the　braking　process,　the　indirect　adaptive　fuzzy　H-infinity　control　strategy　is　employed　to　control　the　rotor　speed　of　the　designed　retarder.　The　results　show　that　the　proposed　retarder　has　the　characteristics　of　continuously　adjustable　large　torque　in　full　speed　section,　sensitive　control　process　and　constant　speed　intelligent　control.