Abstract:On the basis of seven year fixed position observation in Youxi Ecosystem Experimental Station, the nutrient cycle in Chinese fir young plantation ecosystem was studied and the compartment models of N 、P 、K cycle were established. The results were as follows: The total quantities of N、 P、K accumalated in a 7 year old Chinese fir plantation ecosystem were 7308.46, 2022. 96 and 130290. 14kg/hm2 respectively, in which about 99. 73% was stored in the soil compartment. The annual absorption of N、P、 K was 52. 2kg/hm2 with 22. 62kg/hm2 of them ratained, 29. 58kg/hm2 of them returned. The input through hydrologic way into the ecosystem and the output through runoff out of the ecosystem were 15. 92kg/hm2 and 9. 23kg/hm2 respectively. And thus, the net accumulation of ecosystem was 6. 69kg/hm2.The transformations of N 、P、K and results of fertilization in four compartments of ecosystem within 0-10 years were diseribed quantitatively and the balance points at the time when they reach a stable state were calculated.