Abstract: Breaching of barrier dam is in the way of gradually breaching and the dam-break floods are closely related to the breach evolution. Based on the MIKE 11 DB model and Xie Renzhi's empirical formula, the dam-break flood simulation under the typical barrier dam breaking scheme of the Yarlung Zangbo River is carried out. On this basis, the influence of breach evolution form and breaching duration on the dam-break flood is discussed. The research shows that the simulation results of MIKE 11 DB model and Xie Renzhi's empirical formula are similar. The assumed 2/3 dam breaching scheme can be used as the safety threshold for dam-breaking flood calculation. The breaching evolution form and duration have a certain influence on the dam-break flood, and the flood peak of linear breaching is 15.3%-19.5% larger than that under non-linear breaching. The shorter the breaching duration is, the larger the flood peak is, and there is a nonlinear relationship between them. The size and duration of breaching are greatly affected by the earth quality of dam-body. This study further deepens the understanding of the dam-breaking flood of the barrier lakes, and can provide technical reference for the flood control and rescue decision of the barrier dam breaching.