Abstract: The DC resistance characteristics of grounding grid directly affect the safe operation of power systems. The electrical conductivity, corrosion behavior, and interface characteristics of metal materials are key factors determining grounding effectiveness. Based on multi-physics coupling theory, an equivalent circuit model for grounding grid considering material differences and a numerical calculation method for resistivity time-varying characteristics were established. Through systematic analysis of the resistance characteristics of copper-based materials, steel-based materials, graphene metal alloys, and stainless steel materials, the influence patterns of different materials on grounding grid performance were revealed. Research shows that the DC resistivity of graphene metal alloys is 94.2% lower than that of traditional galvanized steel, and the contact resistance of copper-based materials increases by 12.5% for every 10 nm increase in oxide layer thickness. Microscopic mechanism analysis reveals that material grain boundary density, surface morphology evolution, and electric double layer structure are the fundamental factors affecting grounding resistance.