Wheel sensor and falling-off detection device, method and system of wheel sensor

The invention discloses a wheel sensor and a falling-off detection device, method and system of the wheel sensor. The device is characterized in that a plurality of eddy current displacement sensors are arranged on a first side surface, a plurality of eddy current displacement sensors are arranged on a second side surface, the first side surface is opposite to the side surface of a steel rail web, and the second side surface is opposite to the upper surface of a steel rail bottom. A plurality of eddy current displacement sensor probe connecting lines of the first side face are parallel to the first side face, at least one eddy current displacement sensor is arranged on the center line of the first side face, and at least one eddy current displacement sensor is arranged on at least one of the left and right sides of the center line; a plurality of eddy current displacement sensor probe connecting lines of the second side face are parallel to the second side face, at least one eddy current displacement sensor i