The invention discloses a conditioner for increasing organic carbon in soil. The conditioner is prepared from, by weight, 22-35 parts of humic acid, 5-12 parts of animal feces, 4-12 parts of carbonized bacterium rod powder, 8-20 parts of plant ash, 1-6 parts of a seaweed fertilizer, 5-10 parts of straws, 2-6 parts of wormcast, 9-19 parts of an NPK fertilizer, 5-10 parts of carbonized rice husks, 1-3 parts of an EM bacterial agent, 2-5 parts of attapulgite, 2-3 parts of a carbon enzyme, 3-6 parts of polyaspartic acid, 0.01-0.03 part of rare earth lanthanum and 2-4 parts of EDDHA chelated iron.The conditioner can effectively increase the content of organic carbon in soil, is expected to establish a reliable and stable soil organic carbon database, can improve soil, activate solid nutrientsin the soil and improve the absorption of nutrients by the soil, and can agglomerate and bond soil particles and improve the aggregate structure of the soil to make all the nutrients have no antagonistic effects in the soil and balance minerals and nutrients in the soil.