Abstract: Aiming at the over load braking problem of heavy vehicle, a permanent magnet eddy current retarder was proposed as an auxiliary braking apparatus, which is based on the principle of permanent magnet eddy current braking. The retarder can adjust the braking torque. The suction characteristics of the permanent magnetic disk and the eddy current disk were analyzed by using finite element method, and the braking torque adjusting mechanism was designed. The numerical analysis model was established. The electromagnetic field distribution was analyzed by using the finite element simulation software JMAG-Designer, and the relationship between the braking torque and the rotational speed was obtained. According to the analysis of temperature influence on the electromagnetic characteristics of the eddy current disk, the variation law of the braking torque with temperature was obtained by the numerical simulation method. A retarder prototype of Φ485 mm×255 mm was tested. The simulation data was compared with the test data at different air-gaps, and the retarder braking characteristic with different eddy current disks was studied by the bench test. Test results show that the simulation data and test data agree well at low speed. The continuous braking characteristic test shows that the increased surface temperature of the eddy current disk is 158℃ and the brake torque decreases by 34.8% in 82 s.