Taizhou Bridge is the first three-tower two-span suspension bridge with the main span over 1 000 m in the world. The structural system of the stiffening girder is complicated and unique. Improvement and innovation have been made in detailed structure design of the stiffening girder based on Runyang Bridge according to the structural character of three-pylon two-span suspension bridge. In this paper, the structural system, structure design, structure calculation, manufacturing and erection of the stiffening girder are introduced.