Abstract: Driving mechanism of drought is the theoretical basis of understanding drought, both scientifically and for making effective drought-resisting policy. The forming processes of meteorological drought, hydrological drought and agricultural drought and the relationship among them are analyzed. A theoretical framework of the driving mechanism for drought evolution is established by adopting the "driving force-pressure-state-response" model. Key problems such as the principle factors of drought evolution, the driving mechanism of drought evolution, the methods of analyzing evolution rule and response of drought under changing environment are discussed.