Abstract: Based on the experiment of the national "863" special project, the diurnal variation of the stomatal conductance was demonstrated, as well as the variation in the whole growth season. Relationships, under controlled irrigation, between stomatal conductance and environmental factors such as soil moisture, temperature difference between leaf and air, vapour pressure deficit, air temperature and carbon dioxide concentration were analyzed. Stomatal conductance was simulated. Results show, diurnal variation of stomatal conductance was different under different soil moisture conditions; the reduction range of stomatal conductance at noon was enlarged with low soil moisture. The stomatal conductance varied with the soil moisture during the growth season, and recuperated after irrigation or rainfall. The leaf-air temperature differential influences the stomatal conductance most significantly. As far as the air temperature and carbon dioxide concentration are concerned, there are high efficient regions. Taking leaf-air temperature differential into consideration, Leuning-Ball model was revised, which was helpful to interpret the field experimental data.