In various factors that influence the concrete structure durability,coupling corrosion between reinforcement and concrete has been become the important destructive factors in existing concrete structures.Based on the previous test results to 14 corroded RC beams under different corrosion level of concrete and steel bar,the performance of the corroded RC beam under the concrete-reinforcement coupling corrosion is studied.According to those results,estimate methods on flexural capacity under different concrete-reinforcement coupling corrosion are proposed.In this study,effective estimate methods are found out through experiment,which can provide technical reference new thought for flexural capacity evaluation and strengthening design in RC beams under the concrete-reinforcement coupling corrosion,and also have some theoretic guide for practice.