The invention discloses an automatic aligning device for train couplers and a rail train rescue method. The automatic aligning device for the train couplers comprises a cam disc fixedly connected witha train coupler buffer shell; a first notch, a second notch and a third notch are formed in the peripheral surface of the cam disc; an air cylinder is arranged on the outer side of each notch correspondingly, and the three air cylinders communicate with a train air pipe through corresponding air supply pipelines; and each air supply pipeline is provided with a valve, and each valve is controlledby a three-position control switch to be opened and closed to enable only one of the three air cylinders to be kept in a ventilation state. The technical problem of automatic coupling of the vehicle couplers on the small-radius curve is solved.