The utility model discloses a rapid beam descending mechanism based on a bridge synchronous jacking and overall replacement technology. The beam descending mechanism based on the bridge synchronous jacking and overall replacement technology is characterized by comprising two beam carrying vehicles arranged side by side, son columns are arranged on the two sides of each beam carrying vehicle, a mother column used for replacing the beam carrying vehicles is arranged on the vehicle inside each son column, each of the son columns and mother columns is of a multi-segment steel column butt joint structure, a synchronous jacking device is arranged on the top of each mother column, and cushion blocks are arranged on the upper parts of each son column and each mother column. The rapid beam descending mechanism based on the bridge synchronous jacking and overall replacement technology has the advantages that the design is reasonable, the descending mechanism is simple, efficient, rapid and has high safety, a stable and simple beam descending device is adopted, the situation that a bridge is integrally lowered stably and gradually can be rapidly realized, and the potential safety hazard caused by labor intensity requirement for construction to crushing equipment and sites is relieved.