Box girder supporting system and construction method

The invention relates to the technical field of box girder construction, in particular to a box girder supporting system and a construction method. The box girder supporting system is located between two adjacent bridge piers and comprises: a box girder mold and a supporting frame, wherein the supporting frame is located below the box girder mold, the supporting frame comprises two supporting subsections which can be close to or away from each other, the box girder mold comprises two mold subsections, each mold subsection corresponds to one supporting subsection, the supporting subsections are symmetrically arranged with the connecting line between two pairs of adjacent bridge piers as a symmetric line, each supporting subsection comprises a steel pipe supporting mechanism, the lower end of the steel pipe supporting mechanism is connected with a walking assembly, and the ends, close to each other, of the steel pipe supporting mechanism of the two supporting branch parts are detachably connected through fasten