Train humping marshalling duplex retarder

The invention relates to a train humping marshalling duplex retarder. The problem that no compensation function exists when a retarder breaks down and is disabled is effectively solved. According to the technical scheme, the device comprises a grooved rail with a U-shaped section, the grooved rail is fixed to a train rail through bolts, a front retarder and a rear retarder are installed in the grooved rail and arranged in a spaced mode, the front retarder is located in the coming direction of a train, the rear retarder is located in the going direction of the train, and the front retarder is in an extending state. The rear retarder is in a non-stretching locking state, and when the front retarder is disabled, the rear retarder is unlocked and stretches out to replace the front retarder to work; by means of the method, compensation can be conducted on the disability of the retarder when the retarder has a false roof fault and a dead roof fault, and safe deceleration during train humping marshalling is guarante