Chinese fir (Cunninghamia Lanceolata) is a main afforesting tree species in China. The total area of plantations is about 5 million hectares. Yet, its tree production declined rotation by rotation, and soil degradation is severely. This situation has seriously threatened the sustainable utilization of the limited arable forestland. In order to illustrate the mechanism of Chinese fir plantation soil degradation and find out the effective prevention measures, a permanent research, belongs to hill site condition in Dagang mountain of Jiangxi province, was set out on dynamic variations of soil nutrient content of second rotation of young chinese fir plantation in its growing season. The nine-year-research results showed that, the content of soil organic matter was increasing, the content of available phosphate was decreasing and the content of available nitrogen decreased seriously during the growth processes of the second young Chinese fir. The content of available potass was decreasing before the five years growth, while increasing after five years. The content of exchangeable Ca++ and Mg++ decreased severely.