The negative bending moment at the fulcrum of continuous beam bridge is used to reduce the positive bending moment in the middle of the span, which effectively disperses the stress of each section, and thus increases the span of the bridge. The side webs of fish bellied continuous box girder bridge are streamline in shape, which not only increases the bending and torsional stiffness of the interface, but also has an aesthetic appearance. The development of cast-in-place continuous box girder bridge enables the bridge to adapt to a variety of cross-sectional forms and alignment designs, but at the same time increases the complexity of the structure. Therefore, the precise calculation and adjustment of the fish-belly continuous girder bridge are needed to ensure its safety and reliability. Through an example of fish-belly continuous box girder bridge, the plane and spatial finite element model is applied to calculate, adjust and optimize the bridge structure, so as to ensure that the longitudinal, transverse and bridge panel meet the requirements of stress and crack resistance, and provide reference for the design of similar bridges.