Abstract: 【Objective】Studying the stress distribution of an extra-wide stiffening girder of a concrete self-anchored suspension bridge, during the construction process, could provide theoretical reference for its design and construction.【Method】The shear flexible beam grid method was used to establish a finite element beam grid model in space with a Midas/Civil system. Further, the performance of stiffening girder under loading was analyzed.【Result】 The transverse stress distribution in the top and bottom plates of the stiffening girder demonstrated an obvious non-uniformity. In the process of pre-stressing, the stress on the outer webs of the girder was larger than that on the inner webs. In the process of system conversion, the stress increment on inner webs was larger. It was during the process of system conversion that the stress variations in the top and bottom plates of the stiffening girder were different. The maximum compressive stress in the bottom plate was recorded in the hanger tensioning process. Therefore, in the top plate, the compressive stress reaches a maximum after system conversion, while in the bottom plate, the compressive stress reaches a maximum during the process of system conversion. As a passive tensioning process of the hangers, the application of second-phase constant load could significantly reduce the stress difference between the top and bottom plates caused by the initial hanger tension.【Conclusion】The main reason for the non-uniformity in the transverse stress distribution was investigated to be the axial force in the main cable and the action of pre-stressed tendons. The stress distribution in the stiffening girder could be made uniform by adjusting the number and position of pre-stressed tendons.