Abstract: With coal slime water as the research object and studied the flocculation effect on the concentration coal slime water, flocculant dosage and pH for bioflocculant GSY-9 which was produced by azotobacter chroococcum. The results show that flocculation activity is at its highest when the following conditions are met: slime water concentration 30 g/L and a flocculant concentration of 80 mg/L. The flocculation activity can be up to 82.93% of bioflocculant at the time. Flocculant GSY-9 kept the high flocculation activity at the range of pH 2.0~8.0.The main components of bioflocculant GSY-9 were polysaccharide and protein through the analysis of FTIR. Flocculation experiment of the coal associated minerals indicate that the order of flocculent effect from large to small for bioflocculant GSY-9 on the three kinds of mineral is kaolin, illite and quartz. The further experiment of absorption rate for bioflocculant GSY-9 on miners was showed that the flocculent effect of kaolin and illite were far superior to quartz. Zeta potential curve of minerals indicate that bioflocculant is partly composed of anion groups and its flocculating function is based on bridge not on the neutralizing charge.