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Making use of EMTP, the transient simulation of the currents along the towers and ground wires is performed when the lightning strikes the tower of the power transmission line. The investigation shows that the currents along the towers and ground wires dramatically decrease and can be ignored after 5 spans. With the help of Fourier transform, the method of moment is adopted to calculate the transient coating stress voltage of the pipeline and total electric field in the earth when the underground pipeline runs parallel to or crosses the power transmission line. The approximate formulas of the maximum coating stress voltage along the pipeline are proposed for the situation of crossing, which involve the lightning current, soil resistivity and separation distance between the pipeline and tower grounding structure. Eventually, the proposed method can be used to evaluate the safety distance between the pipeline and tower grounding structure with the lightning electrical strength of the anti-corrosion coating of the pipeline.