NOVELTY - Method for preparing compound organic fertilizer, involves concentrating waste mother liquid produced after hydrolyzing chitosan to produce glucosamine hydrochloride, adding the chitosan into the neutralized liquid, heating the neutralized liquor, adding the mixed enzyme to the liquid, performing enzymolysis of the mixture, removing the enzyme after performing enzymolysis, adding organic compound with trace elements to the mixture, extracting and filtering the liquid, and drying the filtrate to obtain solid fertilizer.    USE - The method is useful for preparing compound fertilizer (claimed) which is useful for improving soil quality and promoting growth of crops.    ADVANTAGE - The method is simple and convenient to perform and converts waste water into fertilizer and does not discharge waste water to the environment, and hence environmentally-friendly.    DETAILED DESCRIPTION - Method for preparing compound organic fertilizer, involves (a) concentrating waste mother liquid produced after hydrolyzing chitosan using concentrated hydrochloric acid (HCl) to produce glucosamine hydrochloride to recycle HCl, and neutralizing the residues and syrup using alkali liquor of potassium hydroxide (KOH), where the neutralized liquid shows slant acidity and has pH of 4-5, (b) adding the chitosan into the neutralized liquid, where the concentration of chitosan is 0.5-1 wt.%, and completely stirring and dissolving the chitosan in the neutralized liquid, (c) heating the neutralized liquid and adding the mixed enzyme to the liquid, where the concentration of the mixed enzyme is 8-10 wt.% of the chitosan, and the mixed enzyme comprises one or more acid proteolytic enzyme, cellulose, papain and lysozyme, performing enzymolysis of the liquid at 40-50 degrees C for 2-3 hours, and removing the enzyme after performing enzymolysis, (d) regulating the pH of the liquid to 5-6 using alkali liquor of KOH, and simultaneously adding the organic compound with trace elements to the mixture, and (e) extracting and filtering the liquid to 120-150 microns, and micro-flowing the liquid after the liquid is diluted to 5-10 microns, where the filtrate is used as fertilizer, or the filtrate is dried to obtain solid fertilizer. An INDEPENDENT CLAIM is included for fertilizer, which is prepared by the above-cited method.