To estimate evapotranspiration rate near a trench covered with turf at Terrestrial Environment Research Center (TERC), University of Tsukuba, we used the Penman method. For evaluating the actual evapotranspiration, potential evaporation needs to be corrected by a reduction factor (f). In TERC, the reduction factor has been determined by Nakagawa (1984). This value was estimated under the condition that the soil surface was covered with pasture. To investigate whether the reduction factor for pasture can be possible to use for the turf site, we compared the evapotranspiration estimated by Penmen method, energy balance/eddy correlation method and energy balance/Bowen ratio (EBBR) method. EBBR was investigation at turf site (Meteorological Research Institute). Since the evapotranspiration estimated by Penman method using the reduction factor for pasture agreed with the evapotranspiration estimated by EBBR, the reduction factor for pasture can be possible to use for the turf site.