This study evaluate the performance of vertical axis hydrokinetic turbine (VAHT) - Helical Blade using duct system. Experimental study has been performed in the open channel with measured current speed of 0.7 m s−1, 0.9 m s−1, and 1.1 m s−1. Rotational speed and torque were measured to obtain the performance factor (C P ) and tip speed ratio (TSR). The gain of current speed has good response on rotational speed and torque. VAHT - Helical Blade using duct system has greater C P than non-duct system at three different current speed. The maximum C P is 0.44 reached on TSR of 2.92. The addition of duct system has good response on C P of VAHT - Helical Blade due to increasing current speed around the turbine.