Current density is the key parameter of cathodic protection system design for the reinforced concrete，but how to select the current density parameter for contaminated concrete in a wet environment，there is no relevant research in China. We carry out the research of current density based on laboratory condition，determine the current density parameter of the concrete contaminated by salt in a wet environment，on this basis can form a design of reinforced concrete sacrificial anode cathodic protection system，and apply the scheme in a reconstruction wharf project in Zhanjiang Port to solve the problems of high chloride ion content in pile foundation concrete and serious corrosion of steel bars. The results show that the protective effect of this scheme is good. The protection distance of the intertidal zone can extend to 1 m above the water，protection distance of the under mud zone can extend to 18 m under the mud.