Abstract: Nutrient input from throughfall and its loss through the runoff of three small watersheds covered by Phyllostachys pubescent stands were monitered for study on nutrient cycling in southern China during the period from 1986 to 1989. Results indicate that the concentration and the amount of nutrients from throughfall are close relative to the throughfall amount, and show an obvious seasonal variation. The relative abundance of nutrient from throughfall is K+Ca2+Mg2+NH4+-NNO3--NPO43-. The dynamics of the amount of nutrients lost through the run-off in the small watershed correspond to the seasonal variation of the run-off amount. The relative abundance of nutrients of run-off is K+Mg2+NH4+-N plus NO3--NPO43-. Besides the amount of throughfall and run-off, the bamboo growth character, soil microbial activity and human being measures are the main factors which affect the inputs and outputs of nutrients in a bamboo ecosystem. The GM (1,1) model for predicting the K input amount with throughfall in a year at Miaoshanwu experimental site has been established.