Increasing the efficiency of water use by crops continues to escalate as a topic of concern because drought is a restrictive environmental factor for crop productivity worldwide. Greater yield per unit rainfall is one of the most important challenges in water-saving agriculture. Besides water-saving by irrigation engineering and conservation tillage, a good understanding of factors limiting and/or regulating yield now provides us with an opportunity to identify and then precisely select for physiological and breeding traits that increase the efficiency of water use and drought tolerance under water-limited conditions, biological water-saving is one means of achieving this goal. A definition of biological water-saving measures is proposed which embraces improvements in water-use efficiency (WUE) and drought tolerance, by genetic improvement and physiological regulation. The preponderance of biological water-saving measures is discussed and strategies identified for working within natural resource constraints. The technology and future perspectives of biological water saving could provide not only new water-saving techniques but also a scientific base for application of water-saving irrigation and conservation tillage. Increasing the efficiency of water use by crops continues to escalate as a topic of concern due due drought is a restrictive environmental factor for crop productivity worldwide. Greater yield per unit rainfall is one of the most important challenges in water-saving agriculture. by irrigation engineering and conservation tillage, a good understanding of factors limiting and / or regulating yield now now provides us with an opportunity to identify and then precisely select for physiological and breeding traits that increase the efficiency of water use and drought tolerance under water-limited conditions , biological water-saving is one means of achieving this goal. A definition of biological water-saving measures is proposed which embraces improvements in water-use efficiency (WUE) and drought tolerance, by genetic improvement and physiological regulation. The preponderance of biological water -saving measures is discussed and strategies identified for working within natura l resource constraints. The technology and future perspectives of biological water saving could provide not only new water-saving techniques but also a scientific base for application of water-saving irrigation and conservation tillage.