Objective To study the corrosion behavior of anti-sulfer lean alloy steel P110SS in high temperature environment containing low H2S and high CO2. Methods The corrosion rates acquired by weight loss test of P110SS were studied using high temperature and pressure autoclave in the simulated corrosion environment based on acid oilfield in West China. Combined with SEM, EDS and XRD, the features of corrosion products were analyzed. Results The corrosion rate of P110SS diminished with the raise of temperature in single CO2 environment. The corrosion rate was 0.35 mm/a at 210 ℃. The same regular pattern appeared when 6 kPa H2S was joined. The corrosion rate was 0.74 mm/a at 150 ℃. And the scales on the steel had a two-layer structure. The inner layer consisted of fine-grained FeCO3 and the outer layer was mainly composed of FeS. When H2S partial pressure increased to 165 kPa, the corrosion aggravated and it presented the opposite law of corrosion rate. The corrosion rate was 2.78 mm/a at 210 ℃. The main product was iron sulfide. Meanwhile, the corrosion rate decreased when the corrosion time was prolonged to 2160 h. Conclusion The mechanism of the above-mentioned variations was discussed according to the analysis on characteristics of corrosion products in different conditions. In single CO2 environment, the inner corrosion scale generated at high temperature, which was flawless carbonate, could protect the substrate preferably. It showed the same regular pattern owing to the domination of CO2 when 6 kPa H2S was injected. The inner FeCO3 scale was fine. With the H2S partial pressure increased to 165 kPa, the corrosion process was controled by H2S and CO2. The corrision rate rose notablely due to the poor protection effect of loose and worn iron sulfide.