NOVELTY - Preparation of microbial soil improver comprises taking Lactobacillus acidophilus, Streptococcus faecalis, and Lactobacillus plantarum, adding to anaerobic culture medium, taking Candida utilis, adding to aerobic culture medium, taking Rhodopseudomonas palustris, and adding to photosynthetic bacteria light line culture medium; adjusting liquid cell concentration to 106/mL, mixing prepared culture mediums, anaerobic fermenting, and adjusting pH to 3-4; and filtering and clarifying.    USE - Method for preparing microbial soil improver (claimed).    ADVANTAGE - The soil improver has high safety, strong pertinence, and low cost, provides strains at different culture fermentation conditions, decomposes and transforms soil cropping residual material, enhances soil urease activity, improves soil fertility and water retention, has breathable performance, improves soil physical and chemical properties, balances soil microflora, and has micro-ecological effect.    DETAILED DESCRIPTION - Preparation of microbial soil improver comprises: (A) taking 1 wt.% Lactobacillus acidophilus, 1 wt.% Streptococcus faecalis, and 1 wt.% Lactobacillus plantarum, adding to anaerobic culture medium, weighing anaerobic medium comprising molasses, water, dipotassium phosphate, yeast extract, and soybean at mass ratio of 35:60:0.1:-0.4:4.5, taking 1 wt.% Candida utilis, adding to aerobic culture medium comprising water, molasses, urea, and yeast extract at mass ratio of 60:35:4.5:0.5, taking 1 wt.% Rhodopseudomonas palustris, and adding to photosynthetic bacteria light line culture medium having light intensity of 3000-4000 lx and comprising water, molasses, dibasic potassium phosphate, yeast extract, potassium dihydrogen phosphate, calcium chloride, magnesium chloride, and ammonium chloride at mass ratio of 60:35:0.5:1:0.5:1:1:1; (B) adjusting liquid cell concentration to 106/mL, mixing 1 wt.% prepared culture mediums, anaerobic fermenting for 20 days, and adjusting pH to 3-4, where feedstock culture medium comprises molasses, water, dipotassium hydrogen phosphate, and magnesium sulfate at mass ratio of 35:6:0.5:1.5; and (C) filtering and clarifying.