Abstract: Dike breaking is a type of frequent disasters in China. It often causes flood flows outside the dike and water level fluctuations in the river channel. So far, numerical models are widely used to simulate dike-break flooding, while direct observations from field surveys and physical models are rather limited. In this study, physical experiments have been conducted in a large laboratory flume to simulate propagations of dike-break induced flood waves in flooded area and flow fluctuations in river channel. Variations in water level and discharge were measured and investigated by using a pressure sensor array and two acoustic doppler velocimetries. The results show that: a) flow in the river channel has little influence on the propagation of the dike-break flood waves, while it has remarkable effect on water level distribution; b) in the channel the dike-break induced water dropping caused asymmetrical waves, which propagated slowly upstream with large amplitudes and fast downstream with small amplitudes; c) at the initial stage of dike-break flooding, the rate of flow through the breach varied over time, it was gradually approaching a steady state, and the steady flow rate was related to the difference in discharges at the upstream and downstream sections. The experimental results would provide useful and reliable information for analysis of dike-break flow dynamics and verification of numerical models and for the benefit of flood and disaster control in river management.