The invention relates to a connecting structure of concrete floating docks. The connecting structure comprises a plurality of floating boxes (10), every floating box (10) comprises a concrete casing wall (20) and rubber (30) embedded in the concrete casing wall (20), longitudinal locking parts (40) penetrating through the floating boxes (10) are arranged in wallboards positioned on the concrete casing walls (20), and the adjacent floating docks (100) are connected to be a whole through the floating boxes (10). By enabling the longitudinal locking parts penetrating through the floating boxes to be arranged on the concrete casing walls, floating box structures are greatly simplified, the whole floating docks are more attractive and more convenient to install, the rubber arranged in the floating docks is convenient to process, the adjacent floating docks can move in a left-and-right mode relatively so as to be suitable for the actual accurate position and be more convenient to install and dismantle, and accordingly the effect of protecting a floating bridge is achieved well; simultaneously, compared with other connecting modes, the connecting structure can absorb more energy of various sea waves so that the floating docks are safer and more stable.