The medium-to-deep acidic gas wells in Shenmu Gas Field produce fluids containing CO₂/H₂S, with chloride (Cl^-) concentrations in the produced liquid reaching as high as 30 000 mg/L and wellbore temperatures up to 100 ℃. These conditions pose severe corrosion risks to the downhole tubing strings. To address this, a high-temperature and high-pressure autoclave was used to simulate the operating conditions of the tubing strings within the wellbore. The corrosion behavior of N80 steel was studied under different temperatures (20 ~ 100 ℃), CO₂ partial pressures (0.5 ~ 2 MPa), and H₂S partial pressures (0 ~ 0.7 MPa). The micromorphology and composition of the corrosion product films were analyzed to identify the main controlling factors for tubing corrosion. Additionally, the safe service life of the tubing was assessed based on the corrosion rate. The results indicate that the corrosion of N80 steel is extremely severe, and temperature is the primary controlling factor affecting the corrosion of tubing and casing. When the operating temperature is 80 ℃, the minimum safe service life of N80 steel is 7.3 years. In the coexistence environment of CO₂-H₂S-Cl^-, there are competitive and synergistic effects between CO₂ and H₂S. A small amount of H₂S preferentially forms a denser FeS, which inhibits the formation of FeCO₃. However, high concentrations of H₂S accelerate CO₂ corrosion. Meanwhile, Cl^- damages the corrosion product films and accumulates in pitting corrosion pits. The findings provide data references and theoretical support for assessing the safe service life of tubing strings and formulating corrosion protection strategies in CO₂-H₂S-Cl ^- environments.