Abstract: On the basis of the operator-splitting finite element method, a numerical model for 2-D unsteady flow in a midchannel is presented in this paper. The model can successfully solve the problem encountered in calculation on hybrid operators and is suitable to complex boundaries. Moreover, the coupling of propagation equation with continuity equation for solving the free surface is used, which has a better stability and higher accuracy. The algorithm presented in this paper is verified in calculating the unsteady flow in the channel between the ship locks in the Three Gorges project and the result is satisfactory and helpful in optimizing operation modes.