Abstract: The variations of differences between the evapotranspiration and precipitation in the grassland ecosystem were studied to reveal the water circulation and the productivity in the grassland under the climate change conditions.Based on the climate data of 38 stations throughout the Inner Mongolian steppe during 1960 to 2004,the spatial and temporal variations of differences between the evapotranspiration and the precipitation during April to August were studied,by using Penman-Monteith formula.The results showed that the main spatial anomaly feature of the differences between the evapotranspiration and the precipitation during warm season was coincidently high or low.The steppe could be divided into four anomaly regions in accordance with differences between the evapotranspiration and the precipitation.With times lapse,the differences between the evapotranspiration and the precipitation showed a declining tendency during past 45 years.

Key words: Steppe, Steppe, Evapotranspiration, Spatial and temporal variation, Difference between evapotranspiration and precipitation