Abstract: On the basis of farmland water balance principle, this paper presents a simulation approach to simulate whole process of occurrence. expanding and mitigation of drought events. Simulated results and indices characterized drought event process are analyzed statistically. According to the experimental data about the effect of water shortage in different crop growth periods on crop production sensitivity, the drop of crop production is evaluated quantitatively and the degree of drought event is determined reasonably. It is valid that the simulation results basically fit with the actual cases.