A bioflocculant-producing bacterium was isolated from soil and identified as Serratia ficaria. Using optimized culture conditions a flocculating activity of 95.4% was obtained. It was found to be effective for flocculation of a kaolin suspension over weakly acidic pH (5-7); divalent cations (Ca2+ and Mg2+) enhanced the flocculating activity, while the co-presence of Al3+ and Fe3+ resulted the negative effect. Measurements of zeta potential revealed that charge neutralization played an important role in the flocculation. It could flocculate a variety of real wastewaters, including river water, brewery wastewater, meat processing wastewater and soy sauce brewing wastewater. The bioflocculant was also used to treat pulp effluent, and the removal rate of color and chemical oxygen demand (COD) were up to 99.9% and 72.1%, respectively, which were better than traditional chemical flocculants.