In order to measure a wind turbine performance on a complex terrain that fails to satisfy the IEC standard, we should evaluate a flow correction factor which is the ratio of wind speeds between two points. In this study, we have compared the flow correction factors for 16 principal azimuthal directions between actual measurements and CFD results. From March in 2005 to February in 2006, wind speed and wind direction were measured by using two meteorological. And we calculate unsteady wind fields using highly accurate CFD method combined with both large eddy simulation and geographical information system. As a result, in 6 of 16 directions, the flow correction factors obtained from measurements differ from that obtained using CFD by only 〜10%.