A fixing device for the formwork at the end of a reinforced concrete box culvert for highways, which is arranged at the end of the box culvert, and the end of the box culvert is provided with a water stopper, including a fixing frame (1), a steel bar connecting rod (6), and a tension screw (2), characterized in that: the fixing frame (1) is a cage frame with a trapezoidal cross-section made of steel bars, one end of the cage frame is provided with a gap (19), and one end of the steel bar connecting rod (6) is connected to the steel bar The structural longitudinal reinforcement (7) of the concrete box culvert is welded, and the other end is welded with a threaded sleeve (3). The lower bottom and the upper bottom of the trapezoidal cage frame are finally fastened on the fixture with nuts (5). The fixing device of the invention has the advantages of simple structure, low cost, light weight, fast and convenient use, good template fixing state, reusable, can well protect the waterstop from damage and deformation, and can ensure the level of the waterstop advantage of degrees.