To explore the Spatial-temporal distribution of total phosphorus in the channel from Poyang Lake to the Yangtze River,and identify the main influence factors on the water quality between the hydrological natural rhythm and sand mining,the temporal and spatial variation of the total phosphorus monitoring data of Laoyemiao,Xingzi and Hamashi were statistically analyzed,combined with the regional pollution acceptance.The results show that：（1）due to the different amount of water entering the lake,the self purification capacity and pollutant carrying capacity of the water body change,which leads to the periodic fluctuation law of the total phosphorus index of the main section in the channel from Poyang Lake to the Yangtze River,that is to say the index in the wet season is better than that in the dry season;（2）from Laoyemiao to Xingzi,the total phosphorus concentration shows an optimization trend;the same indicator from Xingzi to Hamashi shows a deterioration trend;（3）sand mining in Poyang Lake has some impact on the section water quality,but its essence is the migration of endogenous pollution caused by sediment disturbance,and its impact is smaller than exogenous pollution discharged into the lake.The above conclusions are helpful to rationally analyze the impact of sand mining on water quality.