NOVELTY - Preparing composite amino acid organic liquid fertilizer, by filtering fermentation industrial waste water, vaporizing, condensing and then crystallizing filter liquid to obtain primary crystallized and mixed slurry, separating liquid and solid of slurry, obtaining sulfate and primary mother liquid, vaporizing and crystallizing primary mother liquid to obtain secondary crystallized and mixed slurry, cooling and crystallizing the secondary crystallized and mixed slurry, performing liquid-solid separation and then separating out sulfate crystal.    USE - The method is useful for preparing composite amino acid organic liquid fertilizer using cheap fermentation industrial waste water as raw material (claimed). The water-insoluble substance produced during the process is useful as protein complementary feed for the ruminant.    ADVANTAGE - The method is cost-effective and enables preparation of high-value, high-fertilizer-effect composite amino acid organic liquid fertilizer, without using expensive bean dreg, dried blood, starch and other acid-alkali chemical preparation. The fermentation industrial waste water can be recycled completely, and has wide applicability. The method does not discharge any substance, hence does not cause environmental pollution.    DETAILED DESCRIPTION - Method of preparing composite amino acid organic liquid fertilizer using cheap fermentation industrial waste water as raw material, involves filtering fermentation industrial waste water and separating into filter slag and filter liquid, vaporizing and condensing the filter liquid, controlling the process such that vaporization amount is 25-35% of the filter liquid amount, making the condensed liquid to be saturated solution of the sulfate, vaporizing and crystallizing the condensed liquid, controlling the process such that vaporization amount is 20-35% of the filter liquid amount, obtaining the primary crystallized and mixed slurry, after separating liquid and solid for the primary crystallized and mixed slurry, obtaining sulfate and primary mother liquid, carrying out secondary vaporizing and crystallizing processes for the primary mother liquid, controlling the process such that the vaporization amount is 25-30% of the mother liquid amount, obtaining secondary crystallized and mixed slurry, carrying out normal cooling and crystallizing processes for the secondary crystallized and mixed slurry, carrying out liquid-solid separation when the temperature of the mixed slurry is less than 30 degrees C, obtaining sulfate and secondary mother liquid, making the separated secondary mother liquid stand for 1-3 hours, separating out sulfate crystal, and obtaining amino acid organic paste fertilizer and composite amino acid organic liquid fertilizer.