Small box girder prefabricated core mold self-dismantling device and using method

The invention relates to a small box girder prefabricated core mold self-dismantling device and a using method. The self-dismantling device comprises a bottom mold trolley arranged on a prefabricated concrete small box girder bottom plate, a core mold assembly, a connecting rod assembly and a supporting assembly, wherein the core mold assembly and the connecting rod assembly are arranged in a prefabricated concrete small box girder. The connecting rod assembly is fixedly connected with the core mold assembly, and rotation contraction of the core mold assembly is achieved through contraction of the connecting rod assembly. The supporting assembly comprises a floor supporting unit, a retractable supporting unit and a supporting beam, and the floor supporting unit is connected with one end of the supporting beam; the retractable supporting unit is connected with the other end of the supporting beam. The retractable supporting unit is used for supporting the supporting beam on a bottom plate of the prefabricated