A depth-averaged 2-D numerical model for unsteady tidal flow in estuaries is established based on the finite volume method on orthogonal curvilinear grid. The 2-D shallow water equations are solved by the SIMPLER algorithm technique. Taking Jiangyin waterway of the Yangtze River as a study example, we apply the moving boundary and “condensation” technique to the numerical simulation of the two-dimensional tide flow and solve the problem of mobile boundary with the water level. The calculation and its verification show that the calculated processes of tidal level and current coincide fairly well with the field data, and the flow field of calculation is reasonable. The depth averaged velocity data and grid data are transformed to colorized velocity profile in AutoCAD for intuitive analysis.