As a basic unit of soil structure and an important site for the soil organic carbon, soil aggregate plays an important role in maintaining the soil quality and sustainable development of ecological environment. In order to understand the soil aggregate stability and organic carbon distribution, 4 typical natural grasslands including meadow steppe, warm steppe, steppe desert and desert steppe in Ningxia were studied. The results showed that the content of mechanical-stable aggregates and water-stable aggregates of meadow steppe, warm steppe and steppe desert indicated a decreased first and then increased trend with reduction of grain size. And the content of mechanical-stable aggregates took on the decreased first and then increased trend, while the water-stable aggregates took on increasing trend with reduction of grain size in desert steppe. The mechanical-stable and water-stable aggregates of meadow steppe and warm steppe were dominated by macroaggregates (>0.25 mm) in 0-10 cm, 10-20 cm and 20-40 cm soil layers, while the water-stable aggregates of steppe desert and desert steppe were dominated by micro-aggregates (<0.25 mm). The mean weight diameter (MWD) and geometric mean diameter (GWD) of mechanical-stable aggregates and water-stable aggregates and the soil aggregate organic carbon content showed that the meadow steppe and warm steppe were significantly larger than steppe desert and desert steppe. Aggregates of >0.25 mm made the largest contributions to soil organic carbon reaching 43.86%, 59.26%, 58.89% and 58.02%, 54.03%, 57.15% in meadow steppe and warm steppe, respectively. Aggregates of <0.25 mm made the largest contributions to soil organic carbon reaching 60.37%, 55.86%, 54.33% and 75.61%, 78.34%, 78.74% in steppe desert and desert steppe, respectively. The results showed that the meadow steppe and warm steppe were more stable in soil aggregates than steppe desert and desert steppe, and they were more beneficial to soil organic carbon accumulation.