[Objective] During the normal operation of metro lines, due to incomplete rail-ground insulation, metro that adopts AC (alternating current) traction power supply system can cause electromagnetic interference on adjacent metallic oil and gas pipelines. Therefore, it is necessary to study the external electromagnetic interference problem caused by metro AC traction power supply system. [Method] Taking the parallel section of a metallic oil and gas pipeline in Guangzhou and Guangzhou Metro Line 22 as example, a coupled model of the metro tunnel and the pipeline is established to simulate and analyze electromagnetic interference on the pipeline. The electromagnetic induction voltages, ground potentials, and coating tolerance voltages of different segments of the oil and gas pipeline with varying angles to the tunnel are calculated, and the main influencing factors of electromagnetic interference are analyzed. [Result & Conclusion] Under the format of AC traction power supply system, the actual voltage endured by the pipeline coating is the difference between the voltage on the surface of the internal metal pipeline and the ground potential in the external soil. The induced voltage amplitude generated by the metro tunnel on metallic pipeline surface is more than 10 times the amplitude of soil ground potential, with the electromagnetic induction voltage between the pipeline and the metro being the main factor causing electromagnetic interference on the metallic oil and gas pipeline. The parallel section of the metallic oil and gas pipeline and the metro tunnel is the main area generating electromagnetic interference. Adding return line can significantly reduce the electromagnetic induction voltage on the metallic oil and gas pipeline, and the position and quantity of the return line have a significant impact on reducing electromagnetic interference.