The invention relates to the field of bridge erection machines, in particular to a rotating mechanism of a segment beam bridge erection machine. The rotating mechanism comprises a shell and a machinebody. A press plate is arranged on the inner side of the shell. First telescopic rods are arranged between the top end of the press plate and the shell. A drive mechanism is arranged at the bottom ofthe press plate. The machine body is arranged at the bottom of the drive mechanism. Limiting mechanisms are arranged on the left side and the right side of the drive mechanism. A transmission mechanism is arranged between each limiting mechanism and the press plate. Clamps are arranged at the bottom of the machine body. According to the rotating mechanism, through the arrangement of the limiting mechanisms, when the machine body does not need to rotate, the machine body can be fixed, the machine body is prevented from shaking, and stability of the machine body is guaranteed; through the arrangement of the drive mechanism, rotating of the direction of the bridge erection machine can be achieved, the trouble of re-mounting is avoided, time is greatly saved, workloads are reduced, and the direction of the bridge erection machine can be rotated more easily; and through the arrangement of a fixed block and a second telescopic rod, a connecting column can be fixed, and the machine body keepsstable.