One strain of Bacillus SP. from the activated sludge is able to produce a stable and efficient bio- flocculation. The flocculation properties and application of this microbial flocculants in wastewater treatment are studied. The results show that the optimum flocculation can be reached in conditions as follows: above pH 7.0, the dosage of coagulation aid CaCl₂ is 5.0 % , the flocculants dosage is 0.2 % , and the centrifugal condition of flocculants broth is 4 000 r/min min and last for 30 min. In the optimum flocculation condition the strain boasts obvious coagulation efficiency in wastewater treatment with produced bio- flocculation.