Active bacteria from activated sludge in Tangjiaqiao sewage treatment plant were enriched, cultivated, separated and purified, and their degree of activity tested. Structural characteristics of the microbial flocculant produced by the activated bacteria were analyzed using coloration reaction and Fourier transform infrared spectrometry. The results show that the most active bacterium is saccharomycetes with a flocculation ratio reaching as high as 95%. Yellow crystal microbial flocculent was obtained through fermentation cultivation, separation and purification from these saccharomycetes. Results of the coloration reaction and infrared absorption spectrometry indicate this microbial flocculent is a type of sugar in which there are numerous functional groups.