Through a self-designed experimental device according to hydrodynamic conditions of backwater area of branch of Three Gorges Reservoir, the experiment was carried out to study the effects of reynolds number and turbulent flow on the vertical distributions of algae and its suspension and gathered behavior in different water depths. In the condition that water temperature is 20℃, illumination is 5000 lx and there are enough nutrient concentrations in water, the experiment results showed that Cyanophyta cells are mainly in the depth ranging from 0.2 m to 0.8 m when average flow velocity is within 0-0.005 m/s and reynolds number is within 0-1750 while Bacillariophyta cells are mainly in the depth ranging from 0.2 m to 0.8 m when average flow velocity is within 0.1-0.5 m/s and reynolds number is within 35000-175000. Compared to Cyanophyta and Bacillariophyta, a considerable part of Chlorophyta cells could suspend in the depth ranging from 0.2 m to 0.8 m when flow velocity is within 0-0.05 m/s and reynolds number is within 0-17500.