Abstract: The corrosion behaviors of P110 steel at the stimulated environments of oil field are systematically studied with electrochemical impedance spectroscopy (EIS) and polarization curves. The results show that the corrosion rate is gradually reduces with the increase of experimental time. The tendency of corrosion reducing rate becomes very slow as 72 hours of experimental time arrived. The phenomena similar to passivation for P110 steel will be taken place on the anodic polarization curves. When Tafel slopes of the cathodic polarization curves change greatly, the tendency of cathodic reaction for P110 steel is different. EIS results of P110 steel indicate that the polarization resistance increases gradually and the electrode reaction are controlled by both diffusion and activation in comparison with activation only at the beginning.