This paper characterizes the temporal evident in characteristic flow and water level from selected hydrological stations in the Ganjiang river tail channel over the period 1956-2014.The Mann-Kendall test and moving average method were used to analyze for trend，interannual variability was characterized.The main causes of the obsverved patterns in water level were investigated among the variables catchment riverbed deformation，upstream runoff change and Poyang Lake water level changes.The results indicate that the characteristic flow of the Ganjiang river tail channel mainly appeared a upward trend，especially in the year and month minimum flow mainly appeared a significant upward trend.The characteristic flow of the Ganjiang river tail channel mainly appeared a downward trend，especially in the year，month average and lowest water level mainly appeared a significant downward trend，upstream segment decreased significantly than the downstream segment.In recent years，the Ganjiang tail river channel appeared obvious undercutting，river volume increased significantly.The river bottom line appeared sharply cut in the main stream，the main branch，the south branch，upper reaches of the middle branch.The main reason for the water level decline is the river bed cut，followed by the Poyang Lake water level decline.