Abstract:[Abstract:] The new version of relevant specifications for Highway Bridges and Culverts puts forward fine research requirements for multi-support pre-stressed concrete cast-in-situ box girder structure. Based on the cast-in-situ box girder structure of a project, the longitudinal loading of single-girder model and the loading method of multi-section influence surface of curved grillage model are respectively used to carry out fine research, and some attentions and optimization suggestions are put forward for the design of cast-in-situ box girder.