We isolated flocculants-producing bacteria F2 from soil. It shows high and stable flocculating activity for Kaolin clay suspension. In order to increase yield of flocculants, we need determine the optimal obtained time. We measured the changes of several parameters using shaking flask experiment, including flocculating- rate, the content of polysaccharide, protein and glucose. It’s showed that the optimal obtained time of bio-flocculants is 21 h. And we built the model about the production of bio-flocculants. Through the comparison of experimental data and the corresponding calculated values from the models, we found that the data joint well and the model can provide theoretical basis for Industrialization of bio-flocculants.