The invention discloses a construction technology for prefabricating a corrugated steel web PC I beam into a combined box girder bridge. Each combined box girder segment in a combined box girder of the combined box girder bridge is formed by connecting two corrugated steel web PC I beams. The construction technology comprises the following steps: Step I, prefabricating the corrugated steel web PC I beams: pedestal prefabricating construction, installation of a soffit formwork, installation of a reinforcement cage in a bottom plate, installation of a corrugated pipe in the bottom plate, installation of a positioning bracket and erection of a side formwork, installation of a corrugated steel web, pouring of concrete on the bottom plate, installation of a top plate molding template, installation of the reinforcement cage in a top plate, pouring of concrete on the top plate, and stretch-drawing of a cable in the bottom plate; Step II, displacement and erection of the corrugated steel web PC I beams; Step III, lengthways wet joint construction; Step IV, stretch-drawing of a cable out of the bottom plate and system conversion. According to the invention, the processing steps are simple, the design is reasonable, the implementation is convenient, the construction period is short, the construction quality is high, pedestal prefabricating and the positioning bracket are combined to complete bridge prefabrication, and the construction quality of the combined box girder bridge can be effectively ensured.