Research on pollutant fluxes of inflow and outflow is an essential prerequisite to establish water quality prediction model of Lake Poyang, and strengthen the management of pollutants receiving capacity threshold in the water function zones of Lake Poyang and Yangtze River. This paper estimated the influxes and outfluxes of total phosphrous(TP), ammonia nitrogen(NH₃-N), permanganate index (COD_Mn) of Lake Poyang, analysed their spatial-temporal variations and main influencing factors, based on appropriate estimation methods, and characteristics of pollution sources for inflow(8 main rivers) and outflow of Lake Poyang, using the synchronous monthly water quality and quantity data during the period of 2008-2012. The results showed:(1) Point source was the main source for TP, NH₃-N of outflow and Le'an River inflow, and for TP of Changjiang River inflow. Therefore, applying monthly instantaneous flux as monthly average flux is more accurate for estimation. For other pollutants at the monitoring sites, applying the product of instantaneous pollutant concentration multiplying monthly average flow as monthly average flux is more appropriate. (2) During 2008-2012, annual average influxes of COD_Mn, NH₃-N and TP were 304398, 53063 and 9175 t, respectively, and annual average outfluxes were 367436, 45814 and 8452 t, respectively. For annual water quantity and COD_Mn flux, and TP flux and NH₃-N flux of some specific years, inflow values of 8 rivers were smaller than those of outflow values due to the fact that flows and pollution fluxes from the intervening basin, and internal pollutants discharges from sediments accelerated by dredging had not been included in this study. (3) During 2008-2012, both annual inflow and outflow pollutant fluxes showed a wavy variation trend, mainly influenced by water quantity. Higher TP, NH₃-N, and COD_Mn influxes of 8 main inflow rivers and COD_Mn outflux mainly occurred in high-water periods, while higher TP, NH₃-N outfluxes mainly occurred in winter (as in lowerwater periods, the biological purification of wetland plants were inhibited). TP, NH₃-N and COD_Mn influxes were mainly from Ganjiang River, Xinjiang River and Le'an River, while the highest concentration of TP, NH₃-N occurred in Le'an River and Xinjiang River.