An effective flocculant-producing microorganism was isolated from activated sludge which was identified as Acinetobacter baumannii. Its genetic toxicity is checked by the Vicia faba root-tip cells micronucleus test, the result has not demonstrated the genetic toxicity. The best carbon sources and nitrogen sources for flocculant production are glucose and yeast extract, the cultivation time is 24 hours. Addition of Ca2+ could obviously increase the flocculating rate. It has good flocculating effect on Kaolin suspension and sewage with pH at the scale of 8.0.