NOVELTY - A soil-improving bio-fertilizer comprises: grass carbon, organic fertilizer, inorganic fertilizer, porous inorganic matter, trace element, clay and compound microbial agent. The porous inorganic matter is selected from vermiculite, zeolite, medical stone and perlite. The compound microbial agent is prepared by fermenting Bacillus mucilaginosus (CICC23640), Bacillus megaterium (CICC21694), Azotobacter chroococcum (ACCCl1104), powdery Pichiafarinosa (ACCC20025) and Streptomyces microflavus (CICC23627).    USE - As soil-improving bio-fertilizer (claimed).    ADVANTAGE - The bio-fertilizer used several microorganisms with the functions of fixing nitrogen, solubilizing phosphate and solubilizing potassium into the fertilizer, so that the nitrogen content of soil can be increased, the utilization ratio of chemical fertilizer is increased, the soil structure is improved, the crop yield is increased, and the crop quality is enhanced. The bio-fertilizer is highly popular, which not only can realize the use of the waste, increase soil fertilizer effect, but also can reduce the environment pollution, and has good economic benefit and environmental benefit.    DETAILED DESCRIPTION - A soil-improving bio-fertilizer comprises (pbw): grass carbon (200-400), organic fertilizer (200-400), inorganic fertilizer (100-400), porous inorganic matter (50-200), trace element (10-30), clay (50-80) and compound microbial agent (10-20). The porous inorganic matter is selected from vermiculite, zeolite, medical stone and perlite. The compound microbial agent is prepared by fermenting Bacillus mucilaginosus (CICC23640), Bacillus megaterium (CICC21694), Azotobacter chroococcum (ACCCl1104), powdery Pichiafarinosa (ACCC20025) and Streptomyces microflavus (CICC23627). An INDEPENDENT CLAIM is included for preparation of the soil-improving bio-fertilizer involving: inoculating Bacillus subtilis (ACCC03120), Bacillus mucilaginosus (CICC23640) and Bacillus megaterium (CICC21694) respectively in a liquid seed culture medium, culturing three for 18-24 hours at a same temperature of 30-37 degrees C, then inoculating the cultured three bacteria to a liquid fermentation medium with an inoculum size of 10-20 wt.% respectively, culturing them for 3-5 days at a temperature of 30-37 degrees C, then adding grass carbon (1-2 g) into liquid fermentation medium (1 ml), absorbing for 15-30 minutes, drying at 35-45 degrees C, crushing and sieving, finally respectively obtaining microbial agent A containing 3-8x 109 powder viable Bacillus subtilis (ACCC031200 in per gram medium, a microbial agent B containing 3-8x 109 viable Bacillus mucilaginosus (CICC23640) in per gram medium and a microbial agent C containing 3-8x 109 powder viable Bacillus megaterium (CICC21694) in per gram medium; inoculating Azotobacter chroococcum (ACCCl1104) into a liquid seed medium, culturing Azotobacter chroococcum (ACCCl1104) for 18-24 hours at 25-30 degrees C, then inoculating the Azotobacter chroococcum with inoculum size of 10-20 wt.% into a liquid fermentation medium, culturing for 3-5 days at 25-30 degrees C, then adding grass carbon (1-2 g) into liquid fermentation medium (1 ml), absorbing for 15-30 minutes, drying the medium at 35-45 degrees C, crushing, sieving, obtaining a microbial agent D containing 1-5x 109 powder viable Azotobacter chroococcum (ACCCl1104); inoculating the powdery Pichia farinose (ACCC20025) into a liquid seed medium, culturing the powdery Pichia farinose (ACCC20025) for 48-72 hours at 25-39 degrees C, then inoculating the powdery Pichia farinose with an inoculum size of 10-20 wt.% into a liquid fermentation medium, culturing for 3-5 days at 25-30 degrees C, then adding grass carbon (1-2 g) into liquid fermentation medium (1 ml), absorbing for 15-30 minutes, drying at 35-45 degrees C, sieving, obtaining a microbial agent E containing 1-5x 109 viable powdery Pichia farinose (ACCC20025) in per gram medium; inoculating the Streptomyces microflavus (CICC2362) into a solid medium, culturing the Streptomyces microflavus (CICC2362) for 48-72 hours at 25-30 degrees C, adding sterile water to adjust the concentration of the spore to 108 powder per milliliter, then inoculating the Streptomyces microflavus into a liquid fermentation medium with an inoculum size of 10-20 wt.%, then adding grass carbon (1-2 g) into liquid fermentation medium (1 ml), absorbing for 15-30 minutes, drying at 25-30 degrees C for 5-7 days, crushing, sieving, obtaining microbial agent F containing 1-5x 109 viable Streptomyces microflavus (CICC2362) in per gram medium; mixing the microbial agent A, microbial agent B, microbial agent C, microbial agent D, microbial agent E and microbial agent F prepared in the above first to fourth steps respectively with ratio of 1-5:1-5:1-5:1-5:1-5:1-5 to obtain a compound microbial agent; and mixing the grass carbon, organic fertilizer, inorganic fertilizer, porous inorganic fertilizer, trace element, clay and the compound microbial agent based on a certain ratio to obtain the soil-improving bio-fertilizer.