Abstract: In order to explore the optimal water-need rule of glycyrrhiza growth in soil wind erosion area of Loess Plateau, the method of controlling irrigation system was used to carry out deficit irrigation experiment on glycyrrhiza under drought conditions. The plant height, amount of dry matter, leaf area index, net photosynthesis rate and transpiration rate of leaves of glycyrrhiza and soil moisture were dynamically determined in different period of duration. The results showed that there was a significant difference in physiological characters of different treatments of glycyrrhiza with the boost of growing season, the treatment of the irrigation amount 900m3/hm2 for 4 times had the characteristics of higher plant, larger leaf area index, stronger photosynthesis and more biomass. The conclusion is valuable to increase coverage of vegetation and capability of soil against corrosion in soil wind erosion area of Loess Plateau.