Based on the principles of crop evapotranspiration, heat exchange, vapor condensation, bionics for collecting liquid water, and water-saving irrigation, an innovative solution to improving crop water use efficiency: condensing evapotranspiration for irrigation (CEI) was summed up systematically. Low-temperature condition is created to aggregate, condense and harvest evapotranspiration vapor, and then irrigates the soil for root absorption, thus a totally closed water micro-circulation of soil-plant-atmosphere-continuum forms. Condensation and collection efficiency of evapotranspiration vapor, and energy use efficiency are key parameters of the technology. The technology is suitable for a serious water shortage, but energy-rich arid and semi-arid areas. The implementing patterns of this technology are divided into three types, such as condensing vapor by heat exchange between shallow soil and air, conditioner-based dehumidifier in greenhouses and collecting air water by bionics net in open-fields. The key points and directions to be solved in the future are breakthrough of bionics for collecting water, and optimization of system structure and operation process.