Abstract: In order to calculate DC current flowing through transformer's neutral point accurately, the key challenge that hasn't been solved effectively is how to establish the proper conducting soil model. Based on the specified conducting soil model, the influence of model simplification on the earth surface potential (ESP) was analyzed for different soil structure configurations. It is found that simplifications only change the absolute value of ESP, but the influence of ESP difference between the transformer substations can be ignored under certain conditions. Therefore, the criteria and threshold value for selection of conducting soil model reasonably are introduced. The results show that the proposed simplication method can properly evaluate the DC values flowing through transformer's neutral point and therefore provide theoretical references for selection of substations near the HVDC ground electrode.