Flow characteristics of a free-horizontal-axis-turbine (FHAT) current power generation system have been investigated by the use of a volumetric PTV. Three types of FHAT system (S50, SE50, S65) have been tested under the current speed 1.35 knot, 1.5 knot and 2 knot. The width of the blade installed around the body is 50 mm. Based upon the power generation characteristics of the FHAT, the flow features of the blade have been investigated. Among the three models it has been verified that the S65 is the most appropriate for power generations.