Abstract: For the L360QS steel gathering and transportation pipeline, combined with the on-site service environment, a series of physical and chemical inspection methods were used to analyze the causes of corrosion of the pipeline. The results show that the chemical composition of L360QS steel pipeline met the requirements of the standard, and its microstructure was composed of ferrite and bainite. The corrosion layer on the inner surface was a corrosion product of a typical H₂S/CO₂ coexistence corrosion system, and combined with the on-site working environment, it was preliminarily believed that the corrosion of the pipeline was dominated by H₂S. In the early stage of corrosion, a layer of FeS protective film was formed on the surface of L360QS steel pipeline, and under the joint action of CO₂, Cl^-, Ca²⁺ and Mg²⁺, the FeS product film was destroyed, which promoted the formation of FeCO₃ corrosion products.