The invention discloses a biological enzyme water purifying agent. The biological enzyme water purifying agent is characterized by comprising, by weight, 10%-15% of protease, 10%-15% of lipase, 10%-15% of cellulose, 10%-15% of pectinase, 5%-15% of bacillus brevis, 5%-10% of nitration coccus, 0.1%-2% of rosa multiflora extracting solution, and the balance being water being completed to 100%. The biological enzyme water purifying agent is a completely natural biological product. Use of the biological enzyme water purifying agent is free of influence of creature types (such as fishes, shellfishes, mollusks, and plankton) existing in water. The biological enzyme water purifying agent not only cannot cause damage to the aquatic organisms, but also strengthens activity of aquatic organism groups due to the improvement of water environment, can purify the water environment, increases transparency and dissolved oxygen of a water body, largely decreases ammonia nitrogen, biochemical oxygen demand (BOD) 5, and phosphorus, balances saprophytic bacteria community, decreases pathogenic bacteria and native parasites, can remove nutriment such as nitrogen and phosphorus in water, enable algae to lose a growing base so as to retrain growth of the algae, and the function of natural self-purification is recovered.