The change of water and sediment flux and channel morphology of five rivers into the Poyang Lake is of great significance to the study of river tail evolution, low and dry water levels in the lake area, as well as river-lake relations. According to measured data from 1956 to 2018, the changes in water and sediment flux and typical sectional morphology are examined using Mann-Kendall test method. Factors affecting such changes were also investigated. Results reveal that: (1) The water inflow of the five rivers decreased in a small extent. Compared with that from 1956 to 2002, the average runoff of the five rivers into the Poyang Lake decreased by 5.3% from 2003 to 2018. (2) Except from Raohe River, the sediment flux into the lake decreased by different ranges. In particular, the sediment flux in Ganjiang River and Xinjiang River declined by large margins, about 72.3% and 52.6% respectively after 2003. (3) The typical sectional shape of the five rivers changed markedly before 2014, and the cross sections were mostly zigzag. Afterwards, the cross sectional shape gradually returned to normal. (4) Water conservancy project, soil and water conservation project, as well as artificial sand mining are major human factors that affect the sediment flux and channel morphology of the five rivers into the Poyang Lake.