Aiming　at　the　heat　fade　of　the　continuous　braking　and　low　power　density　of　traditional　eddy　current　retarder　(ECR)　for　heavy　vehicles,　a　new　liquid-cooled　and　flywheel-type　eddy　current　retarder　is　proposed.　The　new　ECR　can　keep　a　low　working　temperature　because　of　the　cooling　type.　It　is　assembled　between　the　engine　and　the　clutch,　which　can　effectively　improve　the　braking　power　density.　The　transient　electromagnetic　field　of　the　ECR　is　solved　by　the　finite-element　method,　and　the　braking　torque　characteristic　curve　is　obtained.　The　thermal-fluid　coupling　field　is　analyzed　using　the　computational　fluid　dynamics　method.　Finally,　the　structure　parameters　optimization　of　the　rotor　tooth　is　carried　out.　The　braking　torque　increases　by　14.8%　and　the　weight　of　rotor　tooth　decreases　by　9.5%　after　optimization.　The　test　results　show　that　the　heat　fade　ratio　of　the　new　ECR　braking　torque　is　only　8.6%,　but　that　of　the　traditional　ECR　is　46.7%.