In　order　to　overcome　the　problem　of　severe　thermal　decay　of　braking　torque　in　sustained　braking　of　conventional　eddy　current　retarder　and　save　energy,　a　novel　structure　of　liquid-cooled　self-excited　electromagnetic　retarder　is　proposed.　The　electromagnetic　field　and　the　braking　performance　of　the　retarder　are　analyzed　with　finite　element　method　and　numerical　simulations　on　its　transient　flow　field　and　thermal　field　are　conducted　by　using　finite　volume　method.　The　characteristics　of　the　retarder　are　also　measured　on　a　test　bench.　The　results　show　that　the　simulated　results　well　agree　with　test　data　with　a　braking　torque　up　to　1,　600N·m　and　its　thermal　decay　less　than　5%　in　continuous　braking　condition,　meeting　the　requirements　of　heavy　vehicles.　©,　2015,　SAE-China.　All　right　reserved.