.As part of the efforts to ensure adequate supply of quality water from Danjiangkou Reservoir to Beijing, surface water were sampled from the tributaries of Danjiangkou Reservoir in normal (May), flood (August) and dry (December) seasons of 2014, and characterized for nitrogen and phosphorus contents as specified in the applicable standards. Test results indicated that 1)the organic pollutions in Sihe and Shendinghe rivers were more serious than those in other tributaries, and the concentrations of nitrogen and phosphorus favoured the growth of most algae; 2) total phosphorus (TP), total nitrogen (TN) and dissolved inorganic nitrogen (DIN) were in the forms of dissolved phosphorus (DTP), dissolved nitrogen (DTN) and nitrate nitrogen (NO3-N) in these seasons, respectively; 3) compared with nitrogen, phosphorus was more likely to block phytoplankton overrunning; 4)TN, TP, permanganate index (CODMn) and other ions were positively correlated. These findings provided an important basis for the effective measures taken later on as appropriate to ensure adequate supply of quality water from Danjiangkou Reservoir to Beijing.