In this paper, optimal energy management for a stand-alone hydrokinetic power supply system with a battery storage system is proposed to sufficiently explore hydrokinetic energy for customers at the demand side. The management of power flow aims to optimal energy supply subject to a number of constraints, such as power balance, hydrokinetic power output, and battery capacity. The hydrokinetic turbine is connected with permanent magnet synchronous generator (PMSG), power electronic devices and battery bank. The battery bank is used to store the surplus of energy when the load demand is low and discharges again the stored energy to the load when hydrokinetic power is not sufficient to supply the load. The proposed system can meet the load for every hour of the days without interruption. The average daily load requirement and available hydrokinetic power are calculated for three seasons. In this research, the average daily load requirement of the summer season is chosen because it is the highest in energy consumption from three seasons. The simulation results show that the management of the system is satisfied between available hydrokinetic power and load demand.