Nine conical reactors were divided into three groups according to the stirring intensity:low speed group (300 r/min), medium speed group (600 r/min) and high speed group (900 r/min).After 21 days of culture, mature and stable bioflocs were formed, then rapid transformation test and Biolog-ECO test were carried out. The results show that the biofloc structure of low speed group is loose and the edge is fuzzy; the biofloc structure of medium and high speed groups is compact and the edge is neat; the biofloc size decreases with the increase of shear force, and the biofloc size and proportion are inversely proportional to the shear force.In the process of biofloc culture, the water quality changes and rapid transformation test showed that each group had a good removal effect on NH₄⁺-N and NO₂^--N.Biolog-ECO test showed that the microbial community diversity of biofloc was better than that of the other two groups at low speed. In terms of carbon preference, the utilization rate of amino acids was the highest and that of phenolic acids was the lowest in each group. In addition, there were 19 carbon sources with more than 0.5 correlation coefficient of principal component 1. There were 13 kinds of carbon sources with more than 0.5 correlation coefficient of principal component 2. α-D-lactose, β-methyl-d-glucoside, γ-hydroxybutyric acid, itaconic acid and phenylethylamine can be used specifically by microorganisms in different treatment groups.