NOVELTY - Preparing Trichoderma microbial fertilizer by sweet potato starch waste water, comprises (i) sterilizing sweet potato starch waste water, and inoculating with Trichoderma strains, shaking the flask to obtain a liquid seed; (ii) sterilizing starch waste water, inoculating liquid seeds, ventilating aerobic culture in a fermentation tank to obtain liquid product; (iii) adding a cultured liquid seed or liquid product to a biomass material, and carrying out static cultivation to obtain solid product; and (iv) adding stabilizer and aiding material to liquid and solid product.    USE - The method is useful for preparing Trichoderma microbial fertilizer.    ADVANTAGE - The method: is economical and environment-friendly; highly improves the soil quality, and crop yield; prevents plant diseases; and can process large amount of high concentration waste water generated in the production of sweet potato starch.    DETAILED DESCRIPTION - Preparing Trichoderma microbial fertilizer by sweet potato starch waste water, comprises (i) taking waste water from production of sweet potato starch as a raw material, sterilizing at 115-126 degrees C for 15-30 minutes, and inoculating with conventional agricultural Trichoderma strains, e.g. Trichoderma viride, Trichoderma harzianum, Trichoderma aureoviride and Trichoderma koningii according to the inoculation concentration of 106-107 spores/ml culture medium after being cooled, shaking the flask at 20-35 degrees C and at 120-200 revolutions/minute for 24-48 hours to obtain a liquid seed; (ii) sterilizing sweet potato starch waste water at 115-126 degrees C for 15-30 minutes, or using the fresh waste water without sterilization, inoculating 2-20% of liquid seeds, ventilating aerobic culture in a fermentation tank at 20-35 degrees C for 24-72 hours to obtain a liquid Trichoderma product; (iii) taking waste biomass e.g. ground straws, bagasse, beet pulp or rice hull as a substrate, adding a cultured liquid seed or liquid Trichoderma product to a biomass material according to a two fold or four fold weight, and uniformly stirring, carrying out static cultivation at 20-35 degrees C for 3-15 days to obtain a solid Trichoderma product; and (iv) adding a stabilizer and an aiding material for microbial fertilizer to the liquid Trichoderma product, drying, and preserving at low temperature, adding a stabilizer and an aiding material for microbial fertilizer to a solid Trichoderma product, then grinding and packaging.