NOVELTY - Preparing microbial fermentation liquid from fish skin and fish scale comprises: (a) using the fish skin or the fish scale washed by acid to prepare mother solution of collagen; (b) using the mother solution of collagen to prepare culture medium; and (c) preparing fermentation liquid of the composite microorganism.    USE - The method is useful for preparing microbial fermentation liquid from fish skin and fish scale (claimed).    ADVANTAGE - The microbial inoculum obtained through composite fermentation of the microorganism is capable of supplementing organic substance in soil, supplying nutrients for crop, stimulating the crop to grow, increasing permeability of the soil and improving the soil. Tests show that the bacterial manure has better fertilizer effect and the fertilized crop has better quality.    DETAILED DESCRIPTION - Preparing microbial fermentation liquid from fish skin and fish scale comprises: (a) using the fish skin or the fish scale washed by acid to prepare mother solution of collagen: adding 50-100% of the fish skin or the fish scale washed by acid into water to process enzymolysis for preparing the mother solution of collagen; (b), using the mother solution of collagen to prepare culture medium: uniformly mixing 20-60% of the mother solution of collagen with 1-2% of kelp powder, 3-5% of brown sugar, 0.3-0.5% of fulvic acid, 0.2-0.5% of monopotassium phosphate, 0.5-1% of light calcium carbonate and 31-75% of the water; adjusting pH of mixed solution to 7-7.4 to obtain the culture medium, where the percentage is weight percentage; (c) preparing fermentation liquid of the composite microorganism: (i) preparing first-stage seed liquid: using 32-67% of the culture medium, 5-10% of phosphorus releasing germ, 5-10% of Azotobacter, 5-10% of Bacillus subtilis, 4-8% of Saccharomycete, 2-5% of Lactobacillus, 2-5% of photosynthetic bacteria and 5-10% of Trichoderma according to weight percentage; (b) preparing second-stage seed liquid: inoculating 2-5% of the first-stage seed liquid into the culture medium; controlling the temperature at 30-33 degrees C and agitation speed at 150-180 revolutions per minute; fermenting for 24 hours in an aerobic manner; culturing for 48-60 hours in an anaerobic manner to obtain the second-stage seed liquid; and (c) preparing the fermentation liquid of microorganism: inoculating 10-12% of the second-stage seed liquid in the culture medium; controlling the temperature at 30-33 degrees C and agitation speed at 150-180 revolutions per minute; fermenting for 24 hours in the aerobic manner; culturing for 48-60 hours in the anaerobic manner to obtain the fermentation liquid of composite microorganism. An INDEPENDENT CLAIM is a bacterial manure with microbial fermentation liquid comprising 50-55% of the fermentation liquid of composite microorganism, 18-20% of potassium citrate, 8-10% of urea, 4-5% of monoammonium phosphate, 3-5% of fulvic acid, 0.2-0.5% of diethyl aminoethyl hexanoate citrate and 4.5-16.8% of water according to weight percentage.