Abstract: Drought is a main stress factor that restricts growth and development in plants and inhibits Ca2+ uptake by root. Recent results showed that exogenous calcium could improve the drought_resistant capability, inhibit the production of active oxygen substances under drought stress, protect the structure of cell plasma membrane, maintain normal photosynthesis, and regulate metabolisms of horm one and some important biochemical substances. Moreover, the internal cellular Ca2+ could act as a second messenger to transduct the drought signal, and regulate the physiological responses induced by drought stress.