Abstract: The paper analyzes the responsc of plant growth，physiological process and water use efficiency，etc．on different water conditions under CO₂ concentration raising．The results show that CO₂ raising will produce positive effect on plant growth under water deficient conditions，such as increasing of plant leaf area，dry biomas，and root／shot ratio．Meanwhile，it can improve stoma physiology，reduce water transpiration，raise water potential of plant leaf，and enhance grain yield of crop and the water use efficiency，and compensate the adverse effect of water deficiency on plant growth and water use efficiency．This has an important meaning on water saving and yield increa sing of agriculture．