Abstract: The Shihutang hydro-junction is the third planned cascade project in the middle and lower reaches of the Ganjiang River. Stage change in the sandy bed channel below the dam is not only associated with riverbed downcutting， but also linked to the construction and operation of the Xiajiang hydro-junction in the lower reach. Therefore， it is necessary to demonstrate the fall of stage below the dam to determine the elevation of the lock floor of the lower approach channel and the installed plant. Mobile-bed model tests are used to study the trend and value of stage change below the dam. The research results show that in the first three-year operation， water level declines dramatically; after nine-year operation， the maximum fall of stage is about 1。14 m， then it declines slightly. Meanwhile， the falling value is related to the operation time of the downstream Xiajiang hydro-junction. When the Xiajiang hydropower station is put into use， stage falling below the dam becomes stable rapidly. The shorter the construction time span between the two stations is， the smaller the stage decline below the Shihutang hydropower station is. The findings provide technical support for the design of the hydro-junction and the analytical method is of reference value.