Abstract: Taking the Jinsha River Baige landslide dam on November 3, 2018 as a prototype, the same particle grading material was used, and 7 kinds of test conditions were set up, which considered the cross-sectional shape, position, size, and other aspects of the installed discharge troughs. Under the same condition of controlling the upstream water inflow, the experimental breaching process under each condition was observed to reveal the evolution mechanism of landslide dam breaching and its influencing factors. The results show that the breaching process can be divided into four stages: the initial gestation stage, the erosion stage of the backwater slope, the erosion stage of the backwater steep bank, and the stable equilibrium stage of the riverbed. During the breaching process of different cross-sectional shapes of discharge troughs, the impact range of erosion degree is ranked from strong to weak as natural group, triangular groove, rectangular groove, and trapezoidal groove. For the cross-sectional shape and size as well as the location of the discharge trough, when the width is the same and the depth is lower, the breaching process will be earlier under the influence of the constraints; when the section of the discharge trough is the same and the layout is located on one side, under the influence of the fixed constraints on one side, the breaching width expansion will be smaller than that when the layout is located at the center. The research results can provide a reference for the analysis of failure mechanism and emergency rescue and disposal of landslide dam.