Bridge rotation balance early warning device

A bridge rotation balance early warning device comprises an annular track. The first optical signal receiving board and the second optical signal receiving board are arranged on the bottom face, in the length/width direction, of the bridge, the first optical signal receiving board is provided with a first photoelectric sensor, a second photoelectric sensor, a fifth photoelectric sensor and a reference photoelectric sensor, and the second optical signal receiving board is provided with a third photoelectric sensor, a fourth photoelectric sensor and a reference photoelectric sensor; the traction trolley is arranged on the annular track, and optical signal transmitters corresponding to the first/second optical signal receiving plates one by one are mounted on the traction trolley; and the controller is electrically connected with the optical signal transmitter and the trailer wagon, the input end of the controller is electrically connected with the six photoelectric sensors respectively, and the output end of th