Focusing on the case study of the Beijing Sub-center Yudaihe Avenue Cross-river Landscape Bridge Project， and by analyzing the generation elements of the spatial modeling of the side web plates of the irregular curved surface of the cast-in-place box girders， it is determined that the steel formwork scheme will be adopted for the outer facade of the side web slabs. Through the integrated application of Excel software and AutoCAD software， the high-precision 3D modeling is conducted， providing a basis for extracting the cross-section of curved surface steel formwork processing. While providing the 3D model to the steel formwork manufacturer， the requirements for formwork segmentation， the formwork production scheme， the curved surface unfolding method， and the pre-assembly of steel formwork are elaborated in detail， and the key points of on-site installation and positioning of steel formwork are introduced.