In the event of tsunami during winter, damage can be incurred by tsunami intrusion into rivers such as collision between ice floes and river facilities, ice-jamming caused by deposited ice floes and bank overtopping of ice floes and consequent house damage in residential areas. The objective of this study is to clarify the ice floe behaviors during tsunami and to understand the mechanism which causes river ice-jamming. As the result, it was confirmed that ice-jamming occurred during the time of tsunami undertow. It was also revealed that ice floes were transported at the speed twice higher than in normal cases immediately downstream the ice-jamming point. Analysis by the authors succeeded in establishing a hydraulic experimental model to reproduce tsunami induced ice-jamming in rivers.