Abstract: This paper made a comparative study on the water use of the artificial alfalfa grassland and the natural Stipa bungeana grassland with the method of rapid weighing cut leaves or shoots improved by author in Ningxia Yanchi in 1988. The results showed that the productivity in the very arid alfalfa grassland was very high, but that in the Stipa bungeana grassland with a better soil water content it was very low. The ratio of water consumption by transpiration and by evapotranspiration in the alfalfa grassland was 86.0%,but in the Stipa bungeana grassland it was 40.7%.The water use intensity of the alfalfa grassland was 137.32%, but in the Stipa bungeana grassland it was 88.72%. And there were signs to show that the depth of water use in the alfalfa grassland was deeper than 180cm, but in the Stipa bungeana grassland it did not go over 180cm. The transpiration efficiencies in both the grasslands were basically identical, but the evapotranspiration efficiency in the alfalfa grassland was much higher than in the Stipa bungeana grassland (0.82‰ and 0.54‰ respectively) . After the growth phase, the water deficit in the alfalfa grassland reached -101.8mm, but in the Stipa bungeana grassland it was only -17.6mm.