Movable weir is a major system used to manage water level in a river to secure drinking water, agricultural water, and industrial water. It is critical to safely construct and operate movable weir, in any environmental circumstances. In this study, we performed an unsteady flow analysis, on the movable weir with overflow water depth. The continuity equation, with constant density and incompressible Navier-Stokes equation, were used for the flow analysis. The CFD results were applied for structural analysis, to evaluate the safety of movable weir. According to the analysis results, the movable weir has secured sufficient safety.