NOVELTY - Treating industrial and domestic sewage by active organisms, comprises: feeding cyanobacteria liquid containing dry cyanobacteria into the sewage; feeding a bioactive water purifier, stirring and treating the mixture to obtain an upper flocculate, medium water and a lower precipitate, where the micro-ecological preparation comprises mixed bacteria and liquid culture medium, and the liquid culture medium comprises brown sugar, yeast powder and water; applying a water supplying system of the medium water; and refloating and collecting the upper flocculate, and discharging the lower precipitate.    USE - The method is useful for treating industrial and domestic sewage by active organisms.    ADVANTAGE - The method increases the capability of organisms for hogging massive nutrients to promote the reproduction and growth, so that the active organisms can rapidly absorb and degrade the organic matters in the water body, absorb nitrogen and phosphorus nutrients, heavy metals and other suspended matters in fixed water by a mucus layer and a capsule structure at the surface of cyanobacteria during the development of cyanobacteria, and the active organisms are refloated and collected as the raw materials of organic fertilizers, which enable the water body to be applicable as surface water.    DETAILED DESCRIPTION - Treating industrial and domestic sewage by active organisms, comprises: (i) feeding cyanobacteria liquid containing 0.5-5 g/l of dry cyanobacteria into the sewage, where the addition amount of cyanobacteria liquid is 0.1-1 wt.% of the sewage; (ii) feeding a bioactive water purifier, stirring and treating the mixture to obtain an upper flocculate, medium water and a lower precipitate, where the weight of the bioactive water purifier is 0.01-0.1% of the sewage, the bioactive water purifier comprises chitosan (0.5-2%), citric acid (1-2.5%), micro-ecological preparation (2-4%) and water (balance), where the micro-ecological preparation comprises mixed bacteria and liquid culture medium in a volume ratio of 10-15:100-200, and the mixed bacteria comprise Rhodopseudomonas rutila, Streptomyces jingyangensis and Streptococcus lactis in a volume ratio of 2-3:0.5-1:2-4; and the liquid culture medium comprises brown sugar (5-7%), yeast powder (1-2%) and water (balance amount); (iii) applying a water supplying system of the medium water; and (iv) refloating and collecting the upper flocculate, and periodically discharging the lower precipitate obtained in step (ii).