Abstract: Taking Chaohu Lake's 2020 flood season as an example, a one-dimensional unsteady flow model considering the joint-operation of multi sluice gates was established for modeling flood routing and sluice gate dispatching in the Yuxi-Niutun river network of Chaohu Lake. The model was validated with the actual data from Chaohu Lake in 2020. Results showed that: ①the model reliably predicted the hydrodynamic process in the circular river network downstream the Chaohu Gate, and the dynamic distribution of water in the river network induced by the sluice gate operation was also caught well. ②Tongcheng Gate was a key gate that controls the flood diversion from the mainstream, as its opening can expand flood draining of Chaohu Lake by increasing the flood discharge to the diversion river, but reduce the discharge flow through Yuxi Gate. The increased discharge of Chaohu Gate accounted for about 1/3 to 1/2 of the discharge of Tongcheng Gate. ③Excessive use of the Tongcheng Gate for flood diversion may weaken the flood discharge capacity of the Yuxi Gate and aggravate the flood control pressure of the Niutun River. During the flood season in 2020, due to the timely and appropriate opening of the Tongcheng Gate for flood diversion, 400 million cubic meters of water was additionally discharged, which was equivalent to an average drop of about 0.46 m of the water level in Chaohu Lake. Therefore, operation of the Tongcheng Gate for flood prevention and mitigation should be reasonably used in practice.