Aiming　at　the　seriously　overload　braking　problem　of　heavy　truck,　a　permanent-magnet　retarder　based　on　the　principle　of　permanent-magnet　eddy-current　braking　is　proposed　as　an　auxiliary　braking　device,　whose　braking　torque　can　be　continuously　adjusted.　To　solve　the　problem　of　braking　torque　decline　and　the　magnet　loss　of　permanent-magnet　caused　by　high　temperature　due　to　long-time　braking,　a　scheme　of　magneto-thermal　two-way　coupling　is　adopted　and　a　magneto-thermal　coupled　model　of　the　retarder　is　established　with　the　magnetic　permeability　and　conductivity　of　eddy　disk　as　the　mutual　influencing　factors　in　physical　fields,　and　the　braking　torque　characteristics　of　the　retarder　is　studied　with　consideration　of　the　effects　of　temperature,　providing　theoretical　supports　for　the　optimization　design　of　the　retarder.　The　trial　manufacture　and　subsequent　motoring　bench　test　of　several　retarder　prototypes　with　different　materials　and　heat　dissipation　structures　of　eddy　disk　are　conducted　and　the　results　show　that　with　magneto-thermal　two-way　coupling,　the　simulated　braking　torque　agree　better　with　the　tested　one.　©　2019,　Society　of　Automotive　Engineers　of　China.　All　right　reserved.