Strong electric field will be produced in the earth around the grounding poles when HVDC transmission system operates in ground-return mode, which will influence electrical equipment nearby and the metallic pipelines underground. This paper builds a model of multi-layer soil and a typical soil model on basis of actual distribution of soil around the grounding poles, and then calculates surface potential distribution of typical grounding poles by finite element method. The grounding characteristics of DC transmission grounding electrode and the influence on earth surface potential distribution of the two models are compared. The results show that, the ground resistance and the step voltage around the site are much affected by the soil resistivity where the grounding locates. While the ESP which is within the range of tens of meters, is affected by the deep soil resistivity.