Based on the initially proposed closure scheme, a physical model test study was conducted for the TB Hydropower Project to analyze the hydraulic parameters of the closure gap under different operational conditions, and it was pointed out that the discharge index is the key factor determining the difficulty of river closure. Under the actual field condition before the closure, the numerical simulation method was used to analyze the hydraulic parameters of the river closure. The results shows that under the same inflow rate, a deterioration in the diversion conditions will significantly increase the difficulty of river closure. The river basin development company adopted the mode of controlling discharge to assist river closure, which effectively reduce the difficulty of river closure by decreasing the discharge from the upper cascade power station, thus completing the river closure successfully. Both the measured data in field and the inversion results from model test demonstrate that this mode can provide a successful reference for the design and implementation of similar projects in river basin cascade development.