Oil and gas field surface systems are facing serious corrosion problems of metallic pipelines caused by CO2 and H2S. Although the traditional chip method of corrosion monitoring is feasible, it has limitations in terms of accuracy and real-time performance. In this study, the corrosion of 20# steel in a CO2-H2S environment was systematically evaluated by simulating oilfield wastewater and experimental groups under different conditions (single CO2, H2S, and a mixture of the two) using an innovative electrical resistance probe technique for monitoring corrosion in oilfields. The data analysis reveals the influence mechanism of corrosive medium on the monitoring accuracy of the resistance probe, which provides scientific basis and technical support for improving the performance of the equipment and ensuring the safety monitoring of oil and gas pipelines containing hydrogen sulfide and carbon dioxide.