In this paper, high temperature and high pressure corrosion test was used to simulate the corrosion process of multi-component thermal fluid (CO2/O2/H2O) on oil pipes (N80 steel), casings (J55, TP90H, P110 steel, and transportation pipe-lines (20# steel) in the process of CCUS technology application. The results show that during the entire corrosion process, the oil layer casing and surface casing are corroded most seriously in this environment, and the corrosion forms of these five steel materials in the CO2/O2 environment are uniform corrosion and local corrosion, and the corrosion products mainly consist of FeCO3, Fe2O3, Fe3O4, and FeOOH crystals. These oxides form a double-layer film structure on the surface of the steel. The inner layer is denser and consists mostly of FeCO3 crystals, which has better protection against further corrosion of the internal steel. The outer layer is loose and porous, and its components are mostly FeCO3 crystals. Fe2O3, FeOOH, Fe3O4, and FeCO3 crystals, have poor corrosion protection for internal steel. Due to the difference in corrosion products of the inner and outer film layers, relatively obvious local corrosion appeared on the surfaces of the five steel materials.