Abstract: Dynamic tidal power (DTP) is a new way of tidal energy development, a technique that was first proposed by Dutch coastal engineers. The major structure is a T-shape dam of dozens of kilometers long, with its main axis perpendicular to the shoreline, to produce deformation of tidal waves and a difference in water head on the two sides of dam. The head difference for power generation depends on the size of the dam and is often calculated using a theoretical formula or a numerical model. This paper focuses on predicting the dynamic water head difference across the dam using the Kolkman formula and a 2D tidal flow numerical model. Model results show that the difference between the two predictions are relatively small and the values of Kolkman formula are smaller. This means that the seabed resistance is a minor factor of the DTP for open sea areas and for such areas ignore this term is reasonable. A good theoretical formula can reflect the interacting effect of tides and dam, and the accuracy of water level difference calculation will be improved through mutual verification of the Kolkman formula and numerical method.