The transient impact of AC transmission line on pipeline is summarized, which is divided into line switching and fault states, while the latter, depending on the circuit structure, includes line grounding and breaking, lightning strike on the tower without back flashover and back flashover. The transient inductive and conductive coupling between power line and adjacent oil/gas pipeline were analyzed in this paper. The corresponding equivalent circuits of these transient states were established. The electromagnetic interference of Haixi-Tala 750 kV AC transmission line on the adjacent buried natural gas pipeline of the Wulan section was studied. The induced voltage of the pipeline is relative lower during power line switching. The maximum pipeline-to-soil potentials are 4.3kV and 12.9kV respectively during single-phase grounding and line break fault, and the peak voltages reaches 18.4kV and 37.2kV respectively with a lightning strike on the tower and back flashover. The inductive interference from fault phase current partially counteracts the conductive coupling of the grounding current when back flashover occurs. Solid state decouplers are taken as the protection of the pipeline, then the electromagnetic interference is reduced and its propagation is suppressed. The results can provide technical support and reference for the design of common corridor of transmission lines and buried pipelines. © 2021 Chin. Soc. for Elec. Eng.