Influenced by surrounding environment, performance load and eroded by all kinds of media, the structure of lock gate prone to corrosion phenomena. Therefore, aimed at the situation of gate corrosion, to carry out the appraisal method for gate, a gate corrosion detection rating method is established. Based on the environment characteristics, taking corrosion appearance, coating thickness, the residue corrosion depth and corrosion pit depth as the index to evaluate,provides the judgment and evaluation basis for the lock gate is in need of repair.