Abstract: After observing the water transport at leaf-atmosphere interface of typical crop system ，it is proved that the water vapor transfer flux is determined by the construction of plant community．The variation of water vapor transfer flux at leaf-atmosphere interface of a stable community is not only apparently affected by soil moisture and meteorological condition but also by plant physiological mechanism ．Transpiration velocity has daily variation．The analysis show that the net radiation，saturated-air water vapor balance，air temperature，surface temperature and wind speed have highly significant influence on transpiration(positive correlation)．The net radiation and air temperature are the main factors．Stomatal conductivity of leaf reflects its transpiration velocity and the daily variation of stomatal resistance is the plant response to meteorological condition．Stomatal resistance is strongly affected by soil moisture．By improving growth condition of crop，adjusting stomatal action，harm onizing crop transpiration and water-consuming restriction of photosynthesis，the water vapor transfer at leaf-atmosphere car)．be adjusted and controlled and the water use efficiency of crop can be increased．