Abstract: In order to analyze the evolution law of tailing pipe break, clarify the mechanism of tailing dam break, and reveal the impact characteristics of tailing flow, a large-scale physical model test method is used to study the whole process of piping break of a tailing reservoir. The results show that the scour channel is formed by piping, and then the dam break mode of the upper collapse and lateral scour occurs. The development of the breach has gone through three processes: channel expansion, longitudinal undercutting and transverse expansion. Based on this, a 7-stage dam break process is proposed. The tailing flow velocity decays logarithmically with distance, and the 3-parameter impact force model including impact velocity, density and buried mode is as follows: the depth is proposed based on the power function form, and the dam break tailing flow presents undercutting erosion at the near end of the dam body and deposition at the far end. Due to the change process of flow direction at the turning point, it presents the characteristics erosion at the outer side and deposition at the inner side. Based on this, some suggestions for protection of tailing dams are put forward. The above research results may provide theoretical basis for disaster prevention and mitigation of tailing ponds.