The solk water stable aggregates of different diameter(>4 mm,2~4 mm,1~2 mm,0.5~1 mm,0.25~0.5mm) were gained and determined by drying-wetting sieving method in three kinds of eroded(slightly,medium,severely) ultisols.The paper studied the distributions of organic matter in aggregates.The result indicated that the content of >0.25 mm water-stable aggregate(WSA) took on a falling trend with the enhancing of erosion degree,but the dispersing percent of aggregate(PAD) went up.Small aggregate played an important role after moistened.As to slightly and medium eroded ultisols,the content of their organic matter increased with the enlarging of diameter of aggregate,but it was opposite to severely eroded ultisol.In eroded ultisols,soil organic matter had a marked positive correlation with the content of >0.25mm water-stable aggregates.The contribution of aggregate to soil organic matter is in the sequence of slightly > medium > severely in three kinds of eroded ultisols.