In recent years, a number of earth dams reached or will reach the end of their design life.The possibility of dam-break is increasing under the continuous erosion due to flood overtopping.However,because of the measurement methods and the scale problems, it is still a challenge to predict and forewarn the dam-break events.In order to further understand the earth dam failure process due to overtopping,this paper conducted two experiments in a large flume in the State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University.The flume is 50 m in length, 4 m in width, and 2 m in height, and the idealized non-cohesive homogeneous earth dam was placed in the middle of the flume.Two pressure transducers were deployed to measure the time history of water depth along the flume.In addition, two industrial cameras were used to record the dam break process.Analysis of the experimental data shows that: (1) the process of non-cohesive homogeneous earth dam can be divided into two stages,the feature of these two stages are different.The first stage was"headcut" erosion while the second stages was "surface" erosion; (2) comparisons of the experimental data with the Hanson and Hunts empirical formula indicates that Hansons equations coincided well about 184s but Hunts formula has the similar trend about 250 s; (3) the breach width enlargement was attributable to the side slop collapse, but the side slop collapse happened when the ratio of Bw/Bt reached to a critical value, which was 0.94 in these two experiments but it may be the function of D50, moisture content, flow velocity and so on.The result of this paper can provide theoretical reference for other dam-break experiments and numerical simulation.