System analysis and prediction of phosphorus cycling in the ecosystem of secondary oak forest was carried out in the hilly region of Southern Jiangsu Province.The main results indicated that the total amount of phosphorus in the ecosystem of 45-years-old oak forest was 3205.213kg·ha -1 ,of which about 97.6% was stored in the soil compartment and only 2.4% in the vegetation. The trees only used a little amount of total phosphorus in the ecosystem.The phosphorus dynamic showed that the total amount of phosphorus absorbed by the oak increased with years,but the productivity and the phosphorus accumulation rate in the oak ecosystem decreased gradually. However,if increasing of external phosphorus input or decreasing of phosphorus output, the growth of oak would be promoted and the phosphorus accumulation rate in the ecosystem was also accelerated. Therefore, the rational management of the oak forest ecosystem was important and necessary.
