The invention relates to a method for simulating an underground pile foundation of a transformer substation. The method comprises the following steps: 1, establishing an underground pile foundation grounding analytic model; 2, applying the underground pile foundation grounding analytic model into a compound grounding system containing conventional grounding conductors and the underground pile foundation; 3, by adopting analysis tools, under the condition that the underground pile foundation is taken into consideration, analyzing the performance of the whole comprehensive grounding system. Compared with the prior art, according to the method, the resistance reduction and the flow diffusion effect of the underground pile foundation can be analyzed in the design stage, the method can be applied to the performance analysis of the comprehensive grounding system containing the traditional grounding conductors and the underground pile foundation, the design accuracy is improved, and the follow-up transformation and improvement are avoided.