The growing demand for electrical energy is one of the most important subjects today. Decreasing amount and environmental effect of fossil fuels does not seem to surmount this challenge. Renewable energies give a good perspective to be an alternative to fossil and nuclear-fueled power plants, in order to meet growing demand for electrical energy. Hydropower is well known in this category. Hydrokinetic energy technologies are relatively new than other hydropower systems. In this work has been investigated these kinds of hydrokinetic energy, and given some detailed information about current base of hydrokinetic. It has tried to give some knowledge in order to familiarize with the hydrokinetic turbine and generator. The selection information of a suitable turbine has been mentioned.