Abstract:A simulation model of stomatal response to change of environmental water status was set up based on the works on the mechanism of stomatal movement. The variations of leaf conductance, water potential and turgot pressure in guard cells, subsidiary cells and the other cells or tissues in leaf with leaf-air vapour pressure difference and soil water potential have been calculated by our model. The calculated results fit very well with the data from experiments. The different patterns of leaf transpiration variation with the difference between leaf-air and vapour pressure can be explained quantitatively.