Effect of different environment factors on processes of plant transpiration can be simulated by combining stomatal conductance formula, Penman-Monteith formula and soil water limiting models. From the numerical simulation of potted peach（Prunus persica var. nectarina Maxim.）we found that the main weather factors influencing peach canopy transpiration rate are solar radiation, air temperature and air humidity. Plant responds to weather factors by changing stomatal conductance. And the diurnal variation of transpiration is mainly caused by the diurnal variation of weather factors. Soil water conditions can also affect stomatal conductance significantly, and farther affect plant transpiration rate. By numerical simulation we also found that the amount of plant transpiration does not always increase with the increasing of leaf area. For peach, the amount of diurnal transpiration reaches maximal value when leaf area index is about 4. The simulation values of stomatal conductance and transpiration rate were found to conform with the actual values on the whole, which showed that the transpiration rate of peach canopy with different leaf areas and under different environmental factors can be simulated by mathematical method.