Abstract: The channel-storage increment was normally divided into three parts including backwater increment, ice increment in the channel and on the beach, detention water by ice cover and ice jam based on observations. In order to investigate the major sources of channel-storage increment during ice flood season, a river ice dynamics model was established to simulate channel-storage increment process (e.g. growth and decay processes of river ice). The model was then applied to the river channel from the Sanhuhekou station to the Toudaoguai station located in the Inner Mongolia. Results show that flood detention under beach ice cover is the principle source of channel storage increment, accounting for about 63.44% of the maximum channel storage increment. The channel stem storage increment and river ice share the rest increment, accounting for approximately 26.56%, 10% of total increment.