In order to explore the effect of Eucalyptus plantation on the physical and chemical properties of sediments in surrounding reservoirs and the mechanism of migration and transformation of nutrients and organic matter in the reservoirs, taking the Najiang Reservoir in Eucalyptus plantation located in Nanning, Guangxi as an example, the water content, total nitrogen, total phosphorus, total organic carbon and organic matter in the sediments were measured to analyze the distribution characteristics of nitrogen, phosphorus and organic matter and the correlation between the contents of nitrogen, phosphorus and organic matter. The results showed that: the mass ratio of nitrogen, phosphorus and organic matter decreased with depth in the sediments of Najiang Reservoir, and the average contents of nitrogen and phosphorus in the sediment in August were 2 199 mg/kg and 256 mg/kg, respectively, which were slightly higher than those in December(1 994 mg/kg and 230 mg/kg), the reason in which is that water temperature stratification inhibits the sediments from releasing in summer; the fertilizer applied in the cultivation of Eucalyptus was an important source of nitrogen and phosphorus in the sediments, and pesticides and deforestation after cutting was the main component of organic matter in the sediments; organic pollution index of the sediments was far greater than 0. 05 and its fertilizer pollution belonged to level Ⅲ; the contribution of Eucalyptus to nitrogen, phosphorus and organic matter in the forest water is more significant than that of other forests, which is one of the important reasons for sediment fertilizer pollution.