The invention belongs to the technical field of soil conditioners and especially discloses a soil high-carbon-based additive prepared from fermented peanut straw. The additive is prepared from peanut straw serving as a degradation raw material and added with compound bacteria. In the compound bacteria, the ratio of sacillus mucilaginosus to paracoccus denitrificans to trichoderma reesei to succinate filamentous bacterium is (1-5): (1-4): (3-6): (3-6). In the invention, four compound bacteria are used to ferment and degrade the peanut straw according to nutrients in the peanut straw; based on multiple complementary and synergistic effects of the bacteria strains, the peanut straw can be degraded completely in a short time, the prepared soil high-carbon-based additive is capable of improving physical and chemical properties of soil, promoting crop growth and development, inducing crops to enhance resistance, enhancing cold resistance, drought resistance, disease resistance and anti-adversity ability, increasing yield and improving product quality.