The work aims to study the corrosion behavior of different steels containing chromium in the coexistence environment of CO2 and trace H2S and optimize the anti-corrosion design scheme of oil casing in deep wells.The water sample actually separated from oil was used as the corrosion medium to carry out simulation experiments by HTHP autoclave, SEM and EDS technology to reveal the corrosion rate, corrosion product film and characteristics of stress corrosion cracking of four chromium-containing steels in different corrosion environments and establish the optimization design method of oil casing anti-corrosion material selection in the coexistence environment of high CO2 and trace H2S. CO2 dominated corrosion reaction under the condition of high pressure ratio, and the corrosion product was mainly FeCO3. After the addition of trace H2S, the adhesion of the product film of low Cr material was low, resulting in looseness and falling, and FeS was preferentially formed. The corrosion product film on the surface of steels containing chromium presented the "chromium enrichment", which improved the protection of the film. The corresponding corrosion rates of 3Cr steel in the three corrosion environments were 1.965 3, 1.736 1 and 1.159 2 mm/a respectively, which were in a very serious degree, and local grooves appeared on the surface. The product film of 9Cr steel was slightly covered and the corrosion was light. 13Cr and S13Cr had almost no product film coverage, and the corrosion hardly occurred. There was no stress corrosion cracking when 9Cr, 13Cr and S13Cr were loaded with 90% yield stress, and the stress corrosion sensitivity was low. Steel containing chromium has good corrosion resistance, the design scheme of shaft section anti-corrosion material selection 9Cr + 13Cr + Super 13Cr is proposed based on the characteristics of corrosive environment, which effectively reduces the anti-corrosion cost. The research results provide a theoretical basis for the corrosion characteristics and optimal material selection of steel containing chromium in the coexistence environment of CO2 and trace H2S.