Abstract: Present retarders have different problems such as the high price of hydraulic retarder,heat recession of the brake of eddy current retarder and complexity of the control system of self-excited retarder. To overcome these problems,a new retarder—the liquid-cooled eddy current retarder with external rotor was proposed in this paper. Firstly,a prototype of this retarder that could produce up to2 000 N·m brake torque was created. With this prototype,the braking torque was calculated,and the magnetic circuit and temperature filed was analyzed. The internal heat source could be improved. Then,an electromagnetic model based on finite element analysis was built,and the 3-D transient analysis of braking torque and temperature field were conducted. Finally,a contrastive analysis of the simulation results was made.