Through the experimental study of the stress performance of the 12 m span GRC special-shaped inner mold folded linear prestressed rib box girder, the maximum bearing capacity of the box girder was determined, the development of cracks and deflections of the box girder under various levels of load, as well as its failure form and failure characteristics, were analyzed, and the test results were compared with the results calculated according to the current specifications. The results show that the stress performance of the test beam is good, the inner mold and the beam form a unified force whole to work together, and when the load reaches 207% of the design failure load, the failure still does not occur, and there is sufficient safety reserve. Design in accordance with current bridge design codes to meet engineering requirements. GRC thin-walled cylinder core is a promising inner mold for small-span bridges.