Abstract: Abstract: An efficient flocculant producing strain was isolated, which could effectively flocculate suspended matter in piggery wastewater. The sludge from piggery sewage sedimentation tank was selected as the screening material. Screening was carried out by dilution plate method and screening medium. Colonies with smooth, large and sticky surfaces were selected. Then the plate was used to isolate and purify the strain, and then inoculated into the liquid medium. The flocculation rate of swine wastewater treated by bacterial fermentation liquid as index was rescreened. Finally, a flocculant producing bacterial strain FD-14 was obtained and identified by 16S rDNA. First, single factor experiments were conducted on the culture conditions, in order to determine the influence of 4 factors on the flocculation activity, such as culture temperature, pH value, rotational speed and time, L9 (34) orthogonal design was used to optimize the culture conditions of the strain. The culture conditions were optimized: Temperature: 30, 33 and 36 ℃; pH vale: 6.6, 7, 7.4; speed: 120, 150, 180 r/min, and incubation time: 42, 48, 54 h. Then the single factor experiment was used to optimize the carbon and nitrogen source of the medium. By using ultraviolet spectroscopy, infrared spectroscopy, phenol sulfuric acid method and Coomassie brilliant blue method was used to analyze the components of flocculant. Under the optimal conditions, strain FD-14 was cultured and fermentation broth was used as a crude flocculant, which had been applied to practical swine farm wastewater treatment. The results showed that FD-14 was identified as Bacillus amyloliquefaciens based on 16S rDNA gene sequencing. The optimum culture conditions of strain FD-14 were 33 ℃, initial pH value 6.5, rotational speed of 150 r/min, and 42 h incubation. The results showed that strain FD-14 could use starch as an alternative inexpensive carbon source for the fermentation medium, the flocculation rate of 80.80% was not significantly different (P>0.05) from the original standard medium. The effect of substituting inexpensive nitrogen sources was poor; the flocculation rate of the best, ammonium chloride, was 67.38%, which was significantly less than the original standard medium (P<0.05). According to the practical application results on a swine farm, the flocculation rates of the microbial and chemical flocculants of the swine farm wastewater were 79.0% and 62.7%, respectively. The flocculation rate of the microbial flocculant was 16.3% higher than that of the chemical flocculant. Analysis using UV and IR spectroscopy, the phenol sulfuric acid method, and the Coomassie brilliant blue method of flocculant composition revealed that the polysaccharide flocculant was rich in hydroxyl and carboxyl groups. Strain FD-14 mainly secreted 65.96% polysaccharide substances, but the protein content was minimal, so it had strong heat stability. In this study, it could be concluded that bioflocculant-producing bacteria with high flocculating activity and flocculation might be used for flocculation of swine farm wastewater.