The invention relates to a temporary blocking structure of a large-section water-taking-and-drainage box culvert under an operation state and a construction method. Steel pipe piles are arranged between a box culvert top plate and a box culvert bottom plate in a struck mode, wing plates and jacks are arranged in the two sides of a brake box, air bags are inlaid in the wing plates, and the brake box is lowered between the box culvert top plate and the box culvert bottom plate along the steel pipe piles; the wing plates of two sides are jacked out by the jacks in the brake box, after the air bags of the wing plates of two sides are inflated and expanded, the brake box is closely attached to the inner wall of the box culvert, and underwater concrete is poured in the brake box. The steel pipepiles are arranged in the struck mode to serve as 'backers' of the temporary blocking structure, and construction can be conducted under the normal operation state of the box culvert; and the brake box with a hydraulic system is adopted, the air bags serve as assistants, the brake box can be closely attached to a box culvert structure, and the blocking effect is greatly ensured. Compared with a common underwater blocking technology, the influences of the operation water pressure and the flow velocity on the construction method are small, the construction risk is greatly reduced while the blocking effect is ensured, and the temporary blocking structure and the construction method can be applied and popularized in the temporary blocking working conditions of the large-section water-taking-and-drainage box culvert under the operation state.