The invention discloses a preparation method for a special soil conditioner for high earth resistivity environment grounding engineering and belongs to the technical field of a grounding material. The method comprises the following steps: firstly, mixing and fermenting kieselguhr and biogas slurry; eroding the kieselguhr surface, aiming at enriching a surface pore structure of the kieselguhr while absorbing organic matters in the biogas slurry by the kieselguhr; performing anaerobic carbonization, thereby forming a conductive carbonization support structure by the organic matters in the kieselguhr pores; mixing the carbonized kieselguhr, peat and argil, ball-milling and then inoculating earthworm, thereby acquiring a prefabricated mixture and promoting the water retention capacity; with a self-prepared fluid nutrient medium, performing enrichment culture on nitrogen fixation anabaena; centrifugally separating the cultured products; mixing bottom sediment with the prefabricated mixture and humic acid; performing vacuum freeze drying, thereby acquiring the special soil conditioner for high earth resistivity environment grounding engineering.