Numerical simulation of tidal current energy extraction has raised the knowledge about the issue of energy extraction from marine sources. A water channel in laboratory scale is simulated using FLUENT code. FLUENT is a state-of-the-art computer software for CFD analysis based on the finite volume method, and its applications have been over almost the entire fluid dynamic spectrum. FLUENT has been used for tidal energy extraction simulation in this study. A disk, which generates a pressure drop due to energy loss, drives the tidal stream turbine in the model. The fluid model, which can be freely deformed, has been used for the free water surface. Numerical results show that a wake is formed in the back of the tidal flow turbine and an accelerated flow around, especially below the energy generator device is created. It is supposed that the drop of the water surface due to the energy extraction in the model has an important effect on improving the wake of the turbine.