The microbiological influenced corrosion (MIC) behavior of the Cu-Ni alloy with or without Ni-P plating in the sterilized medium and sulfate-reducing bacteria (SRB) solution was investigated. Results show that severe pitting corrosion appeared on the uncoated specimens in both the sterilized medium and the SRB solution when the specimens coated with Ni-P plating were still in good condition. Since the Ni-P plating may offer both barrier and cathodic protection to the base metal. Besides, the structures of Ni-P plating and the passive film on the surface of the Ni-P plating are high uniform and amorphous without any structure defects. The non-crystalline structure may improve the corrosion resistance because it does not have crystalline defects such as dislocation, grain boundary, twin and so on which may cause corrosion easily. It is concluded that corrosion behavior of the Cu-Ni alloy with electroless Ni-P plating was improved greatly.