NOVELTY - Preparing composite microbial fertilizer comprises e.g. preparing the fermentation culture medium, mixing fish meal, corn powder, and brown sugar, crushing, taking fish meal, corn powder, and brown sugar, and removing the impurities in mixed fish meal, corn powder after crushing, mixing brown sugar, mixing the obtained mixed material and water, and adding the obtained mixture material into water, mixing evenly to obtain the fermented culture medium, and activating by adding Bacillus megatenum, Bacillus mucilaginosus,and Bacillus licheniformis strain.    USE - The method is useful for preparing composite microbial fertilizer (claimed).    ADVANTAGE - The fertilizer improves soil nutrition, increase product yield or improves the quality of agricultural products and liquid microbial composite product.    DETAILED DESCRIPTION - Preparing composite microbial fertilizer comprises (i), preparing the fermentation culture medium, mixing fish meal, corn powder, and brown sugar, crushing, taking 60-70%:15-30%:10-15% of fish meal, corn powder, and brown sugar, removing the impurities in mixed fish meal, corn powder after crushing, mixing brown sugar, to obtain mixed material, mixing the obtained mixed material and water in an mass ratio of 4-5:100, and adding the obtained mixture material into water, mixing evenly to obtain the fermented culture medium, (ii), activating by adding strain according to weight ratio Bacillus megatenum, Bacillus mucilaginosus, Bacillus licheniformis in an mass ratio of 1-3:1-3:0.5-1.5, mixing uniformly to obtain mixed fungus liquid and adding to the mixture containing 0.5-1% brown sugar in shake flask with water, controlling temperature at 28-36 degrees C, rotating at the speed of 160-280 revolutions/minute for 1-2 hours. The mixed fungus liquid comprises , Bacillus megatenum SIT4051 (CGMCC NO: 1.1870), Bacillus mucilaginosus SIT4052 (ACCC NO: 10012), and Bacillus licheniformis SIT4053 (CGMCC NO: 1.521), the mass percent concentration of brown sugar and water is 0.5-1%, the mass percent concentration of 0.5-1% brown sugar water and mixed fungus liquid is 3-7:100,(iii) mixing the obtained step (2) mixed fungus liquid and activating, according to quality ratio count, activating the mixed fungus liquid and fermentation culture medium in an mass ratio of 3-10:100, inoculating the mixed fungus liquid in fermentation culture medium, maintaining pH to 6-8, and temperature at 28-36 degrees C, and rotating at the speed of 120- 280 revolutions/minute, fermenting for 15-25 hours to obtain the aqueous composite microorganism fertilizer.