In light of difference in CO2 corrosion behavior of different steel casings, the work aims to explore CO2 corrosion characteristics of conventional steel materials under different corrosion conditions in order to optimize economical CO2 corrosion resistant oil casings. With formation water of actual oilfield as corrosive medium, simulation experiment was performed to oil casings made from different materials. Morphology characteristics of corrosion products on the surface of corrosion samples were analyzed by X-ray diffractometer so as to study the influences of CO2 partial pressure, temperature and test period on corrosion rate of oil casings. With the increase of CO2 partial pressure, the corrosion rate of normal carbon steel and low Cr steel changed significantly; at the CO2 partial pressure of 0.3 MPa, corrosion rate of normal carbon steel was 2.2021 mm/a and 13Cr as low as 0.1052 mm/a, showing no obvious law; as temperature increased, the corrosion rate firstly increased then decreased, corrosion rate of steel N80 and 1Cr steel was far higher than that of 13Cr steel. Corrosion rate of steel N80, 1Cr and 3Cr oil casings increased slightly in shorter test period and decreased significantly as the test period increased continuously; as for corrosion morphology, normal carbon steel sample was subject to serious corrosion and mainly uniform corrosion. There was a small amount of local light spots with local corrosion on the surface of 1Cr and 3Cr steel; the surface of 13Cr steel was smooth, glossy, pitting-free and slightly corroded was. The influence of corrosion rate of normal steel on CO2 partial pressure is more sensitive than that of Cr alloy steel. Temperature and test period have influences on corrosion products on the surface of metal. With the continuous increase of temperature and test cycle, FeCO3 protection film takes shape on the surface of metal. A passivation film takes shape on the surface of steel containing Cr due to enrichment of Chromium, which has inhibited the corrosion rate of oil casings. The research has theo-retical guiding significance on material selection of oil casings in CO2 corrosion environment.