The influence of pH value on corrosion behavior of N ion implanted SUS316L stainless steel, Co Cr alloy, CPTi and Ti 6Al 4V alloy surgery medical materials has been investigated in Hank's solution using electrochemical technology. Experimental results indicate that corrosion potentials of specimens decline, and E b and crevice corrosion potentials of SUS316L stainless steel and Co Cr alloy also decline with decreasing pH value, which results in an increase of the sensibility of local corrosion. The corrosion rates of CPTi and Ti 6Al 4V alloy also increase in Hank's solution with much lower pH value.