The invention relates to a concrete bridge reinforcing design method based on a force rib stress test result. A test system adopted in the reinforcing design method comprises a steel strand, a surface strain gauge, a protective layer concrete chisel-away region, a stress release point, a data acquisition instrument and a cutting machine. The steel strand is coated with the protective layer concrete chisel-away region. The surface strain gauge is stuck to a steel wire at one end of the to-be-tested steel strand along the axis of the steel wires. The stress release point is arranged on a steel wire at the other end of the to-be-tested steel strand, and the point serves as the release point to conduct cutting. The data acquisition instrument is connected to the surface strain gauge through a conductor. The cutting machine cuts off the to-be-tested steel wires at the stress release point. Compared with the prior art, a reinforcing material calculation area result reckoned through the prestressed concrete bridge flexural capacity reinforcing design method based on the force rib stress test result is accurate and reliable, and the method is suitable for flexural capacity reinforcing design of a cracked and damaged prestressed concrete bridge.