Eddy　current　retarder　is　a　kind　of　auxiliary　braking　device　based　on　eddy　current　brake.　To　solve　its　serious　thermal　recession　problem　of　braking　torque,　an　electromagnetic　liquid　cooling　retarder　with　embedded　rotor　was　proposed,　based　on　transverse　electromagnetic　flux.　The　characteristics　of　its　structure　and　working　principle　were　studied.　According　to　regularity　of　eddy　current　distribution,　the　calculation　formula　of　the　braking　torque　was　deduced　by　using　the　electromagnetic　principle.　The　relationship　between　the　braking　torque,　size　of　rotor,　material　of　stator,　excited　current　and　rotor　speed　were　obtained.　Meanwhile　the　correctness　of　the　calculation　formula　was　verified　by　experiments.　At　last,　the　test　of　no-load　loss　torque　and　the　thermal　decay　of　the　electromagnetic　liquid　cooling　retarder　were　conducted　by　test　bench.　The　test　results　show　that　the　structure　of　the　electromagnetic　liquid　cooling　retarder　is　reasonable,　and　it　has　high　power　density　and　small　heat　fading　with　continuous　braking.　©　2018,　Editorial　Department　of　Journal　of　Beijing　University　of　Technology.　All　right　reserved.