The effects on the total nitrogen (TN) and total phosphorus (TP) retention of the inflows and outflows in Wan'an Reservoir, Jiangxi Province were investigated from 2007 to 2009.The results indicated that 1.57×lO⁴, 2.38×lO⁴ and 2.95×lO⁴ tons of dissolved nitrogen were trapped in Wan'an Reservoir in 2007, 2008 and 2009 respectively, and 7.44×10² t, 3.65×lO³ t of TP in 2007 and 2009, respectively.The retention of TP in Wan'an Reservoir appeared negative in 2008, which reflected exogenous input.The retention efficiencies of dissolved nitrogen were the annual average of 32% with the range of 12%-45%, and retention efficiencies of TP were in the range of-89% to 80%.It suggested that the retention efficiency of nitrogen was lower than that of phosphorus except for 2008.The river runoff was the main factor of the seasonal changes of TN fluxes, and the nutrient concentra-tion was the restriction factor on the retention of TP.