Abstract: The relationships between the water-cement ratio of concrete, relative humidity, corrosion state of the reinforcement and the half-cell potential of the reinforcement of a reinforced concrete member are analyzed. Based on the indoor test results of reinforced concrete samples and measured results of some members of Zhanjiang Dock and Tianjin Dock, China, the half-cell potential scope for evaluation of the reinforcement corrosion state of reinforced concrete members of coastal harbors in China is preliminarily presented.