NOVELTY - Carbon-based sustained-release fertilizer comprises cottonseed meal, rice straw, traditional Chinese medicinal residue, attapulgite, fishpond sediment, humic acid raw powder, modified cassava starch solution, diammonium phosphate, potassium nitrate, and perlite powder, where the modified cassava starch solution comprises cassava starch, concentrated vitriol, potassium permanganate solution, sodium hydroxide, borax, sodium selenite, calcium bicarbonate, and water.    USE - As carbon-based sustained-release fertilizer for crop development.    ADVANTAGE - The carbon-based sustained-release fertilizer is rich in nutrients, nitrogen, phosphorus, potassium and trace elements, and suitable for long-term usage, has sustained-release property, and enables excellent nutrient absorbability by plant roots.    DETAILED DESCRIPTION - Carbon-based sustained-release fertilizer comprises 26-28 pts. wt. cottonseed meal, 17-19 pts. wt. rice straw, 14-16 pts. wt. traditional Chinese medicinal residue, 5-8 pts. wt. attapulgite, 20-24 pts. wt. fishpond sediment, 6-7 pts. wt. humic acid raw powder, 4-6 pts. wt. modified cassava starch solution, 7-9 pts. wt. diammonium phosphate, 4-5 pts. wt. potassium nitrate, and 8-10 pts. wt. perlite powder, where the modified cassava starch solution comprises 45-55 pts. wt. cassava starch, 2-3 pts. wt. concentrated vitriol, 4-6 pts. wt. potassium permanganate solution, 3-5 pts. wt. sodium hydroxide, 1-2 pts. wt. borax, 2-3 pts. wt. sodium selenite, 2-4 pts. wt. calcium bicarbonate, and water (suitable quantity). The modified cassava starch solution is prepared by dissolving cassava starch in 2 times water, constantly and continuously stirring the mixture, adding concentrated sulfuric acid catalyst, stirring the mixture for 5-10 minutes, adding sodium hydroxide, gelatinizing the mixture for 15-25 minutes, adding cross-linking agent borax to the mixture, stirring the mixture for 10-20 minutes, adding sodium selenite, heating and reacting the mixture at 60 degrees C for 15 minutes, adding calcium bicarbonate, chelating the mixture at 90 degrees C for 30 minutes, diluting the obtained mixture using 9 times water, stirring the mixture, and uniformly cooling the mixture. An INDEPENDENT CLAIM is included for method for preparing the above-mentioned carbon-based sustained-release fertilizer.