The inverse Lagrangian dispersion analysis method was used with the aim of calculating the evapotranspiration and the H2O source/sink distribution within and over broadleaved Koreanpine forest canopy, using only gradient measurement of microclimate parameters as the input of the model from 1 May to 30 September 2003. The results showed that the model produced agreement between modeled and measured daily daytime evapotranspiration. The total daytime evapotranspiration was equal to 204.88 mm compared with the measured value, 194.26 mm. However, the total calculated evapotranspiration, 298.91 mm, is much higher than the measured result, 240.33 mm. The variation of the source/sink with time and depth were also discussed at the same time.