The invention discloses an automatic transmission, bending and welding integrated device used for large span box beam main reinforcement. The automatic transmission, bending and welding integrated device used for the large span box beam main reinforcement comprises bending platforms, welding devices, transmission devices and rotating devices, wherein the welding devices, the transmission devices and the rotating devices are arranged on the bending platform; the bending platforms comprise N bending platform bodies arranged at intervals, and N is greater than or equal to 2; a welding device is arranged on each bending platform; the corresponded set number transmission devices is N+1, a bending platform is arranged between every two adjacent sets of transmission devices; and two sets of rotating devices are correspondingly arranged at the tail end of the transmission device arranged at the end of the bending platform. According to the schemes of the automatic transmission, bending and welding integrated device used for the large span box beam main reinforcement, labor intensity of workers is lowered, the production efficiency is improved, the actual using effect is good, and production requirements are met; the bending mechanism, the welding mechanism and the transmission mechanism of rebar are combined into a whole, the structure is compact, the volume is decreasing, the automatic transmission, bending and welding integrated device used for the large span box beam main reinforcement is suitable for manufacturing of the large span box beam main reinforcement, standard pieces are adopted, and the cost is greatly lowered.