Based on the analysis of the tidal current turbine's characteristics， a 25 kW stand-alone horizontal axis tidal current turbine is designed. The prototype consists of an optimally designed energy capture device， a split-power mechanical driving unit， and an electrical control system with a battery bank. Digital simulations are conducted to predict the system's working performance， based on the theoretical prediction of the turbine performance and the model analysis of the electro-mechanical system. The sea trial results show that the prototype system runs stably in the actual sea conditions and the maximum power generation reaches the designed power rating. The results clearly verify the effectiveness of the system. The prototype system can be used as a stand-alone power generation device to supply electricity for the users in island area.