Abstract: Aimed to study on whether constant water levels immediate at the upstream of control gates can be maintained in the Middle Route of South-to-North Water Transfer Project, the different unsteady flow transit ional processes are simulated when inflow at the head, openings of control gates and the flow rates divided by outlets are changed simultaneously.The results show that a very long time is needed to reach a new steady state of the flow in the channel under operations of all control gate openings simultaneously and the transitional time needed for the decreasing of gate openings is much longer than that for their increasing.Water levels at the upstream of control gates vibrate to a big extent in transitional processes and can restore to their initial values finally.More studies are needed to find out the methods of gate operation that can fully realize constant water surface elevations immediate at the upstream of sluice gates for real time channel regulations.