The work aims to explore the difference of performance of P110 casing steel passivation film formed at different temperature and find out the temperature that can make P110 casing steel form the most stable passivation film and to know the failure law of the passivation film caused by chloride ions at this temperature. The passivation behavior of P110 casing steel immersed for 4 days in cement extract solution with pH value of 13.0 was studied by polarization curves method, electrochemical impedance spectroscopic (EIS) and Mott-Schottky test. The stability of passivation film formed at low, middle and high temperature (40 ℃, 65 ℃ and 90 ℃) was discussed and the surface morphology of each sample was observed by scanning electron microscopy (SEM). Finally, different concentrations of chloride ions were added into the cement extract solution, and the polarization curve method was used to investigate the failure rules of chloride ion to the passivation film. The corrosion current densities of the specimens at 40 ℃, 65 ℃ and 90 ℃ were respectively as follows: 2.2727×10?6 A/cm2, 4.0452×10?7 A/cm2 and 1.7081×10?5 A/cm2; and the membrane resistance were respectively as follows: 100 100 Ω?cm2, 238 200 Ω?cm2 and 5480 Ω?cm2. The passivation films formed at 40 ℃ and 65 ℃ showed p-type semiconductor feature and the passivation films formed at 90 ℃ showed a bipolar semiconductor feature. With the increase of chloride ion concentration, the corrosion potential of the sample negatively shifted, the corrosion resistance gradually decreased and the corrosion rate increased. When the concentration reached 0.1 mol/L, the film structure of the passivation film was destroyed. The surface of P110 casing steel can form a passivation film after being immersed in the cement extract solution with pH value of 13.0 for 4 days. The corrosion resistance of the passivation film formed in the solution at 65 ℃ is the best and the film structure is more compact which is followed by that at 40 ℃. The films formed at 90 ℃ are the worst. The chloride ion can erode the passivation film and the high concentration of chlorine ion can directly cause the destruction of the stable passivation film.