Abstract: Briefed here in the article are the principle concerning CO₂ corrosion of oil well pipes in the field and the R & D of the low-Cr-containing casing. Detail description is focused on the mechanical properties and the resistance against CO₂/H₂S corrosion-caused-cracking of the economic type anti-CO₂/H₂S corrosion oil casings as the final products of massive production. Furthermore, relevant analysis are made by means of such facilities as SEM（ scanning electron microscope）, X-ray electron energy spectrometer, X-ray diffractometer and stereomicroscope etc., pinpointing the composition of the substance on surface of the said casing resulting from CO₂ corrosion and the anti-CO₂ corrosion mechanism of the casing.