The depletion of fossil energy reserves and environmental issues currently play an important role in developing the concept of renewable energy, so that the search for new renewable energy is carried out very intensively. One type of renewable new energy that has the potential to be developed in Indonesia is the energy of river estuary flows, considering that Indonesia is an archipelagic country.This study, discusses renewable energy derived from the river mouth of the Bedono village of Demak Regency. The results of the observations that have been made, the tidal currents of the river which occur 2 times in 24 hours with an average current velocity at 0.953m/s. The biggest current velocity at 14.00-16.00 is 2.5 m/s and the lowest is 0.5 m/s at 06.00-08.00. Using the Computating Fluid Dynamic (CFD) model simulation and the Darrieus Type H turbine, with specifications; Diameter 1m, chord length 0.1m, turbine length 1 m, number of blade 3 and type of blade Hydrofill: NACA 0018 obtained the greatest power occurs at 14.00-16.00 at 8007.813Watt with a torque of 3540.470Nm and the lowest power of 83.726Watt with torque amounting to 14,663Nm at 04.00-06.00.