Abstract: Since the 1950s, international studies have confirmed the technical advantages of high-voltage direct current (HVDC) transmission projects, such as large capacity, low loss, and high stability. In recent years, due to the reverse distribution of energy demand and resources in China, large-scale long-distance transportation of energy is inevitable. HVDC is especially suitable for large-scale transmission projects such as “west to east power transmission” and “north to south power transmission.” Therefore, a number of HVDC projects have been built in China since the 1980s. However, with the large-scale construction of HVDC transmission projects, the interference effect of HVDC grounding electrode on metal facilities is increasingly prominent, in which the buried pipeline will produce high amplitude of pipe-to-soil potential under HVDC interference. As a result, HVDC interference can cause damage to pipelines, personnel, and related equipment. However, there is no systematic analysis of the causes of high amplitude of pipe-to-soil potential at home and at abroad. Based on the actual engineering parameters, this paper established a calculation model of the high-voltage direct current interference electric field on the buried pipeline and a numerical simulation technology was used to explore the causes of the high amplitude of pipe-to-soil potential under HVDC interference. Moreover, the influence of the distance between the grounding electrode and the pipeline, the type of anti-corrosion coating, the length of the pipeline, and the soil structure on the pipe ground potential under HVDC interference was investigated. Results reveal that the high amplitude of pipe-to-soil potential under HVDC interference is under the joint action of the short distance between the grounding electrode and the pipeline, the high insulation performance of the anti-corrosion layer, the large length of the pipeline, and the soil layered structure with low resistivity at upper and high resistivity at lower.