Provided is an automatic water feeding robot for trains. The movable end of a horizontal movement device is connected with one end of a first telescopic arm through a rotary shaft. A rotation driving device is arranged between the horizontal movement device and the first telescopic arm. The rotation driving device can drive the first telescopic arm to rotate around the rotary shaft. An adsorption device is arranged at the other end of the first telescopic arm, and the first telescopic arm is connected with the adsorption device through a traction device. The traction device can drive the adsorption device to move. A second telescopic arm is installed at the fixed end of the first telescopic arm. The first telescopic arm and the second telescopic arm are each internally provided with a telescopic drive device, and the telescopic drive devices can drive the first telescopic arm and the second telescopic arms to be telescopic correspondingly. According to the automatic water feeding robot for the trains, manual operation is not needed at all, water addition to the trains is wholly controlled through programs, the water addition speed is high, no water resource is wasted, the telescopic arms can determine the three-dimension space position through horizontal movement, rotation and telescoping, and the trains stopped on the two sides of a water feeding channel can both be fed with water automatically by installing the automatic water feeding robot on the water feeding channel of a station.