Abstract: The new method, electric pulse signal transient response method for testing and evaluating corrosion conditions of reinforcement in concrete structures, is speedy and nondestructive with high accuracy. Based on the data of electric pulse signal transient response under the action of galvanostatic pulse collected by computer data acquisition system, the characteristic parameter of the product of resistance and capacitance ( RC ), which reflects corrosion conditions of reinforcement, is calculated. It can be seen from the results of laboratory tests and field monitoring that the value of RC is mainly related to the corrosion conditions of reinforcement, and that the reinforcement is corroded when the value of RC is less than 4.4 s.