There were little works about electrochemical corrosion behaviors that appeared in high H2S and CO2 containing environment. In this work, the electrochemical behaviors of tubular steel API-P110 in buffered acidic NaCl solutions saturated with high H2S and CO2 containing gases, were investigated by potentiodynamic sweep technique. Analysis of the results shows corrosion density declines with increasing CO2 content in H2S/CO2. The corrosion potential of steel moves towards more negatively with the increase of CO2 content in H2S/CO2. In pH 2.9 solution, Passivity appears in high H2S and CO2, but no passivity shows in due to decreasing in high H2S. In pH 5.3 solution, cathodic liming density comes out and increases with the increasing CO2 content in H2S/CO2, however, no cathodic liming density comes out in H2S.