NOVELTY - Producing natural seaweed organic fertilizer, comprises washing seaweed, mechanical crushing, alkali processing, filtering concentrate, drying, complex mixing, screening, carrying out pressurized granulation, detecting, packaging and warehousing. The production method specifically comprises e.g. washing seaweed, crushing, homogenizing, adding alkaline solution in a reaction kettle, carrying out pressurized heating-digestion, removing insoluble component, washing digested slurry, filtering to obtain solid material, drying, compounding with organic-inorganic material, and pelletizing.    USE - The method is useful for producing natural seaweed organic fertilizer (claimed).    ADVANTAGE - The method uses less amount of alkali liquid and does not use enzymatic agent, and uses reaction kettle with relatively low operating environment requirements. The fertilizer contains large amount of non-nitrogenous organic matter, potassium, magnesium, zinc and other multi-mineral nutrients, and also contains specific seaweed polysaccharide, highly unsaturated fatty acid, is rich in cytokinin, auxin and other plant growth regulator, has high biological activity, can promote the absorption of absorption and growth of plant, improves stress resistance of crops, and increases yield.    DETAILED DESCRIPTION - Producing natural seaweed organic fertilizer, comprises washing seaweed, mechanical crushing, alkali processing, filtering concentrate, drying, complex mixing, screening, carrying out pressurized granulation, detecting, packaging and warehousing. The production method specifically comprises (i) washing seaweed, crushing mechanically and homogenizing, (ii) adding alkaline solution in a reaction kettle, carrying out pressurized heating and digestion, and removing insoluble component in the reaction kettle, (iii) washing digested slurry with water and filtering concentrate to obtain corresponding solid filter material, (iv) drying solid material, compounding solid material with other organic and inorganic raw material, and (v) using extrusion pelletizer, detecting products index, and finally weighing and bagging.