Abstract: Saerilficial anode perfomances of 35 steel are measured in seawater and freshwater by invariable current experiment and its feasibility to cathodic piotection of copper tube is analyzed by polarization curves and cathodie protection of copper The results show that 35 steel has well sacrificial anode perfomance. steady working potental and high current efficiency, even and slow dissolution. It has enough driving potential which exceeds 200 mV to protect copper tube. The short-term results indicate that 35 steel has quite well protective effect on copper tube.