Demolition of the old bridge has become a common phenomenon in urban demolition and reconstruction. According to the actual situation of a (18 + 26.4 + 18) m three-span continuous box girder bridge, it is proposed to use Bailey beam and suspender to fix the beam body, and then use the bridge erecting machine to remove the beam body and move to the open area to be broken. The difficulty lies in the adjustment of the internal force of the suspender between the bailey beam and the beam body. The suspender needs to be pre-tensioned before lifting, and the axial force of the suspender needs to be adjusted during lifting. In this paper, the principle of the adjustment of the internal force of the boom and the internal force of the boom at different stages are described in detail for reference. The bridge has been demolished, and the whole process is safe and controllable, which proves that the method is feasible for the demolition of this bridge structure.