The mechanism of corrosion resistance for Cu-30Ni-xRE(x=0~0.213) alloy were investigated by employing electrochemical testing, x-ray diffraction, optical microscopy, scanning electrical microscopy and Energy Disperse Spectroscopy. The results showed that comparison with Cu-30Ni alloy without RE, Cu-30Ni-0.095RE alloy with right amount had decreasing composition segregation of Ni element. This resulted in the decease of corrosion driving force between centre of dendrite and interdendritic. As a result, for Cu-30Ni-0.095RE alloy the corrosion potential increased by 11.0%, and the corrosion current decreased by 37.3%.