NOVELTY - Preparing organic fertilizer using sodium alginate industrial waste residue, involves (a) preprocessing raw materials by crushing the raw materials, mixing potassium dihydrogen phosphate (1-10%) and shell powder (1-10), adding water to adjust water content to 50-70%, and uniformly mixing all the materials, (b) heating the mixed material to 40-50 degrees C, inoculating rot promoting agent, turning mixture after a certain time, maintaining anaerobic conditions every 1-3 days, and ensuring high temperature period, and (c) drying and crushing natural fermented material.    USE - The method is useful for preparing organic fertilizer using sodium alginate industrial waste residue.    ADVANTAGE - The organic fertilizer is prepared within short fermentation period by simple process. The organic fertilizer has high nutrients retention rate.    DETAILED DESCRIPTION - Method for preparing organic fertilizer using sodium alginate industrial waste residue, involves (a) preprocessing raw materials by crushing the raw materials into particle size of 1-10 mm, mixing (per dry weight of the raw materials) potassium dihydrogen phosphate (1-10%) and shell powder (1-10), adding water to adjust water content to 50-70%, and uniformly mixing all the materials, (b) heating the mixed material to 40-50 degrees C, inoculating rot promoting agent, turning mixture after a certain time, maintaining anaerobic conditions every 1-3 days, and ensuring high temperature period, where in the step (a) the raw material is one or more of sodium alginate industrial waste residue, wheat bran, straw, Chinese traditional medicine residue, fruit residue, active sludge, ratio of carbon and nitrogen in the raw material is 20-35:1, and content of one or more raw material is 0-50 wt.%, and in the step (b) water content of the mixture is 50-70%, mixture is fermented for 18-26 days, the rot promoting agents is one or more of bacteria, yeast and fungi, preferably Actinomycetes, and size of the inoculum is 0.5-7%, and (c) drying and crushing natural fermented material. An INDEPENDENT CLAIM is included for use of the above-mentioned organic fertilizer directly or in combination with other inorganic fertilizers to obtain organic-inorganic compound fertilizer.