In　this　article,　a　new　high-torque　retarder　combining　the　effects　of　magnetorheological　fluid　and　eddy　current　is　researched.　The　new　retarder　provides　a　part　of　the　braking　torque　generated　by　the　shear　stress　of　the　magnetorheological　fluid　and　an　additional　braking　torque　generated　by　the　effect　of　the　eddy　current　on　the　rotors.　This　operating　concept　is　realized　by　a　common　magnetic　excitation　circuit　generated　by　a　new　structure　with　several　separated　coils.　The　configurations　and　design　details　of　the　new　retarder,　including　the　structure,　material　selection,　and　magnetic　circuit,　are　discussed.　The　mathematical　models　of　braking　torque　caused　by　the　magnetorheological　fluid　and　eddy　current　are　also　derived.　Then,　a　finite　element　analysis　is　performed　to　verify　the　magnetic　field　design　of　the　new　retarder.　Finally,　a　prototype　is　fabricated,　and　the　relevant　parameters　are　tested.　The　experimental　result　shows　that　the　new　retarder　provides　not　only　a　stable　braking　torque　at　low　speed　but　also　a　great　increment　of　braking　torque　varied　with　rotation　speed,　which　effectively　improves　the　total　braking　torque　compared　with　conventional　magnetorheological　retarders.　©　The　Author(s)　2018.