The invention relates to the technical field of immersed tube prefabrication construction, in particular to a formwork structure based on narrow-space gallery construction in immersed tube prefabrication. The formwork structure comprises a trolley and is characterized by further comprising a formwork, wherein the formwork comprises a top mold fixed at the upper end of the trolley, side molds connected to the two sides of the trolley, upper chamfering formwork bodies connected between the top mold and the side molds and lower chamfering formwork bodies hinged to the lower ends of the side molds, and the lower chamfering formwork bodies are of foldable structures which can retract and extend and are formed by a plurality of sections of formwork bodies. The formwork structure is simple in structure, convenient to operate, capable of effectively adapting to formwork demolding and formwork mold-closing in a narrow gallery space, high in construction efficiency and high in precision, and hasgreat popularization value.