Taking two main tree species, Eucalyptus and Pinus, planted around Tianbao reservoir in Eucalyptus plantation area as the study objects, we compared the water quality characteristics of the distilled water, surface water and bottom water of the reservoir in which the litter leaves soaked. Combined with the water quality in runoff area of the reservoir near Eucalyptus and Pinus forest in spring(March), summer(July), autumn(November)and winter(December)in 2018, this paper analyzed the effects of Eucalyptus Plantation on the black water of reservoir in forest area. The results showed that the soaking solution of Eucalyptus is yellow-brown or even black-brown in color, and its chroma was significantly higher than that of the soaking solution of Pinus. The concentration of tannic acid and dissolved organic carbon(DOC)is 1.14mg/L and 46.40mg/L, respectively, which are higher than that of Pinus. The chroma of water body was positively correlated with DOC and tannic acid, and the correlation coefficients were 0.83 and 0.94, respectively. The organic matter and Mn content of waters flowing into reservoir near Eucalyptus forest area were also higher than that near Pinus forest area. The concentration of Fe and Mn increased to 1.21mg/L and 2.09mg/L, respectively, when the leaves of Eucalyptus litter were mixed with the bottom water of anoxic reservoir.