Assessment of Kuroshio power test site was performed by considering major ruling factors, including in-situ measurement, GIS (Geographic Information System) data base, and ocean flow simulations. Key factors consist of Kuroshio current speed, island wake induced by Kuroshio passing, fishing rights, shipping routes, environmental protection, as well as seabed topography and geological features. Kuroshio current field around Green Island was measured using ADCP and X-Band radar, and was simulated using POM (Princeton Ocean Modeling) and SWEs (Shallow Water Equations) model. Meandering vortex street behind the Island observed by satellite images were numerically reproduced. All ruling factors considered are integrated by the GIS data base. The optimal power test site is thus determined based on the superposition of all influence factors.