Abstract: Studying a high spatial-resolution distribution pattern of observed aboveground biomass of grasslands and its climatic attributions within a continuous geographical area and during a specific time period is crucial for assessing responses of the net primary production of grasslands to climate change, and validating satellite derived and model estimated grassland aboveground biomass. Using statistical data of the grassland investigation in Inner Mongolia during the 1980s and Geographic Information System techniques, we produced a distribution map of the grassland aboveground biomass with a 1km?1km spatial resolution for the typical steppe of Inner Mongolia, and then analyzed the spatial patterns of the aboveground biomass and its relation to thermal-moisture conditions. The grid aboveground biomass has a significantly positive correlation with latitudes and longitudes of the corresponding grids (P<0.001), representing a decreased tendency from north to south and from east to west. The aboveground biomass at meteorological stations has a significantly positive correlation with mean annual precipitation (P<0.001) and a significantly negative correlation with mean annual air temperature (P<0.001) and mean annual aridity index (P<0.001). It is worth to note that in areas with the mean annual aridity index between 1 and 1.5, the aboveground biomass has a very sensitive response to changes of the aridity index. The spatial patterns of the aboveground biomass was therefore shaped under the controls of thermal-moisture conditions: longitudinal distribution characteristics of the aboveground biomass were mainly determined by mean annual precipitation, whereas latitudinal distribution characteristics of the aboveground biomass were influenced by both mean annual air temperature and mean annual precipitation.