Abstract: Rule of accumulation and distribution of particulate organic matter and formation of water stable aggregates were studied by long-term located experiments in the typical black soil region of Songnen Plain.The results show that there are great effects of different fertilization patterns and cultivation systems on the formation of water stable aggregates.＜1mm water stable aggregates is the dominance in fraction of water stable aggregates from cultivated land.Particulate organic C exists mostly in the water stable macro-aggregates,its content decreases with the decrease of particulate levels,indicating that particulate organic C plays an importent role in maintaining the water stability of aggregates in cultivated black soil.