Taking Chaohu close river as research object,using the hydro and ecological dynamics model, the paper probed the effects of water divertsion on both water quality improvement and inhibition of algal bloom,and verified the simulation result through water diversion test. It used mathematical model to calculate the optimal cycle of water diversion and proposed the reasonable measures of integration of hydraulic structures rehabilitation/improvement with water diversion/draining.The results indicated that water diversion can significantly improve the hydrodynamic conditions in urban rivers, make the average flow velocity more than 0.10 m/s, which is higher than the critical flow velocity of phytoplankton growth.The frequency of water diversion should be within 21 days. The calculation result is more reasonable through a water transfer test. Therefore,the scientific and reasonable water diversion can reach the goal of restraining harmful algal blooms to outbreak in summer.