As the pretressed reinforcement of prestressed concrete structure leads to rust, it would bring serious disadvantage effect to load capacity of the concrete members and reduce the reliability of all concrete structure greatly more than that of ordinary steel caused. If the prestressed reinforcement can be detected in time, the prestressed concrete structure would be got effective maintenance. In the paper, magnetic leakage testing method used in ordinary steel detection is applied to test the simulation corrosion bug of the prestressed reinforcement in bridge with nondestructive mode. The result of experiment indicates that in the distance of 100 mm from the concrete surface the magnetic leakage testing method can detect effectively the loss ratio of cross-section more than 20 percent of a hank of prestressed strands caused by a part of prestressed strands corroded to break. At last, the paper also puts forward the experiment problems in existence and the improvement methods.