NOVELTY - Microbiological water purifying agent comprises Saccharomyces cerevisiae CICC No.31015 fermented material, Bacillus subtilis CICC No.21082 fermented material, Brevibacillus laterosporus CICC No.21185 fermented material, Bacillus licheniformis CICC No.23433 fermented material and Lactobacillus acidophilus CICC No.6090 fermented material, and prepared by inoculating and culturing.    USE - The purifying agent is useful for strongly degrading macromolecular organic matter in sewage.    ADVANTAGE - The purification agent: reduces the eutrophication of water; controls or eliminates blue algae outbreaks with obvious effect; can precipitate heavy metals and impurities in the water; is good for recovery; can make water to be clear and transparent; contains large amount of probiotics, which can restrain harmful bacterial in the water; promotes aquatic animal health in water body; and increases cultivation efficiency.    DETAILED DESCRIPTION - Microbiological water purifying agent comprises Saccharomyces cerevisiae CICC No.31015 fermented material, Bacillus subtilis CICC No.21082 fermented material, Brevibacillus laterosporus CICC No.21185 fermented material, Bacillus licheniformis CICC No.23433 fermented material and Lactobacillus acidophilus CICC No.6090 fermented material, and prepared by inoculating and culturing. Preparation comprises taking S. cerevisiae fermented material, B. subtilis fermented material, B. laterosporus fermented material, B. licheniformis fermented material and L. acidophilus fermented material according to ratio of 15-30:5-25:10-25:5-25:25-50, inoculating S. cerevisiae on inclined plane culture medium, then culturing at 28-30 degrees C for 12-48 hours, inoculating B. subtilis on inclined plane culture medium, then culturing at 37 degrees C for 12-48 hours, inoculating B. laterosporus on inclined plane culture medium, then culturing at 35-37 degrees C for 12-48 hours, inoculating B. licheniformis on inclined plane culture medium, then culturing at 37 degrees C for 12-48 hours, and inoculating L. acidophilus on inclined plane culture medium, then culturing at 37 degrees C for 12-48 hours, culturing the strains on 1000 ml conical bottle containing liquid culture medium, placing the conical bottle in a shaking table, culturing at 28 degrees C for 12-48 hours, using blood cell counting plate for counting until number of cells in the strain solution reaches 100 million/ml, and then inoculating on fermentation culture medium containing 26-40 pts. wt. corn powder, 5-19 pts. wt. wheat bran, 16-30 pts. wt. soybean meal, 15-40 pts. wt. pure rice bran, 2.5-4 pts. wt. stone powder, and 2.5-4 pts. wt. calcium hydrophosphate, and then fermenting until the viable cell count reaches 100 million/g in the fermented material, and water content to less than 12.5%. The purification agent comprises 15-30 pts. wt. S. cerevisiae fermented material, 5-25 pts. wt. B. subtilis fermented material, 10-25 pts. wt. B. laterosporus fermented material, 5-25 pts. wt. B. licheniformis fermented material, and 25-50 pts. wt. L. acidophilus fermented material, which are crushed and mixed. The liquid culture medium for S. cerevisiae comprises 1 l 5 degrees Be malt juice, and 15 g agar, and its pH is natural. The liquid culture medium for B. subtilis comprises 5 g peptone, 3 g beef extract, 5 g sodium chloride, 15 g agar, and 1 l distilled water, and pH is 7. The liquid culture medium for B. laterosporus comprises 0.5 g yeast extract, 20 g mannitol, 0.2 g potassium dihydrogen phosphate, 0.8 g dipotassium hydrogen phosphate, 0.2 g magnesium sulfate heptahydrate, 0.1 g calcium sulfate dihydrate, ferric chloride (trace amount), sodium molybdate (trace amount), 15 g agar, and 1 l distilled water, and its pH is 7.2. The liquid culture medium for B. licheniformis comprises 5 g peptone, 3 g beef extract, 5 g sodium chloride, 15 g agar, and 1 l distilled water, and its pH is 7. The liquid culture medium for L. acidophilus comprises 10 g casein peptone (trypsin), 10 g meat soup extract, 5 g yeast powder, 20 g glucose, 1 g Tween 80 (RTM: Polyoxyethylene sorbitan monooleate), 2 g potassium dihydrogen phosphate, 5 g sodium acetate, 2 g diammonium citrate, 0.2 g magnesium sulfate heptahydrate, and 0.05 g manganese sulfate, and its pH is 6.2-6.5.