The invention discloses a method for preparing a carbon-based mineralized active fertilizer. The method includes the steps that forestry and agricultural residues and woody brown coal biomass serve as basic materials, the basic materials and a catalyst formed by mixing and blending powdered rock phosphate, pumice stones, serpentine, medical stone and bentonite are crushed respectively, mixed according to a certain proportion for pelleting and then placed into a carbonation reaction kettle for a reaction, output materials are cooled and then crushed again, wood vinegar, a biological agent and humic acid are added, stirred and mixed, and the carbon-based mineralized active fertilizer is obtained through pelleting. The carbon-based mineralized active fertilizer prepared through a simple and effective method is environmentally friendly, microcellular structures are increased by 20% and above compared with traditional charcoal, the fertilizer contains richer nitrogen, phosphorus, potassium and medium trace elements compared with the charcoal obtained just through biomass, the total quantity of nitrogen, phosphorus and potassium available to plants is increased by 15-30%, the total content of N-P-K is larger than or equal to 10% and above, the content of organic matter is larger than or equal to 36%, the fertilizer contains rich organic acid, the fertilizer consumption can be lowered, and fertilizer efficiency can be improved.