Abstract: Simulation of leaf stomatal conductance (gs) and scaling it up to canopy conductance (gc) were very important for understanding the corn evapotranspiration scaling transformation. Measurements of leaf stomatal conductance (gs) and canopy conductance (gc) were made at a summer corn field. The effect of the photosynthetically active radiation (PAR) and the water vapor deficit (VPD) on gs were analyzed, and the variation of gs was simulated and a model of scaling up gs to gc was developed. Results indicated that gs showed typical diurnal pattern with peaks occurred around 10:00-14:00. The gs increased with the increase of PAR, but decreased with the increase of VPD. And the diurnal variation of gs could be better expressed by the developed gs model using PAR and VPD. The scaling model was developed by integrating to achieve scaling up from gs to gc.