Despite the abundance of rock-fill dams in China, the research on the process of flood propagation resulting from the dam-break remains relatively scarce. This paper presents numerical simulations of flood propagation due to overtopping failure of rock-fill dam under various hydraulic head conditions, based on the coupled CFD-DEM method. The study explores the dynamic characteristics of the dam-break flood, the submerged water depth, and the scope of disaster. The accuracy and effectiveness of the CFD-DEM method in addressing this problem are also evaluated. In addition, the prediction model of flood propagation is established. The conclusions of relevant research provides theoretical support and technical references for the emergency response to dam-break hazards.