Abstract: A strain named BS-5 was screened from river bed sludge. Its metabolin has a high and stable flocculability and can be used as a microbial flocculant through proper culture. After optimizing the cultural conditions, the strain produced a highly activated flocculant MBFBS-5 with a flocculating rate up to 97.5% in Kaolin suspension. Then, the relationship of the time for culture to its flocculability and the distribution of the flocculating activity in culture medium was studied. The thermal stability and the effect of MBFBS-5 dosage and pH value on flocculability were also researched in Kaolin suspension. The results showed that it has such advantages as short culturing time, low dosage, wide pH range and high thermal stability. The results of applying it to the wastewater treatment in beer industry indicated that MBFBS-5 has a high flocculability by which the removal rate of COD is up to 79.2%.