Abstract: Based on the breach process of the clay-core wall sandy dam, as well as the characteristics of dam breach flood propagation and movement, the 2-D numerical simulation of breach area and the coupling simulation of the dam-breach flood of Heihe Jinpen reservoir dam are presented in this paper. The method of DAMBRK is used to calculate gradual dam breach, and the results of DAMBRK model are used in the following simulation. A one-dimensional model is solved by the Abbott-Ionescu six points implicit finite difference scheme. The unit centered finite volume method is adopted to solve a two-dimensional model equation. To achieve the coupling of 1-D and 2-D model, the lateral connections are used to connect the level calculation points and the two-dimensional grid unit of both sides of Heihe River. The 2-D model is developed to calculate and simulate the breach area. The instantaneous water depth and the velocity distribution of the calculation region are given by the 2-D model. Taking the flood with frequency of 0.01% for example, the simulating results, such as water level and discharge process of each cross-section within the one-dimensional river course and water depth profile, velocity vector diagram and submerged range changing process of two-dimensional computational domain are presented by the coupling simulation. The formation process of the breach area includes not only the direct effects of overtopping flow, but also the anti-erosion effect of the spiral flow on both sides in the process of breach. Both flows change inner river and flood evolution of the calculation area in the outer river, which could be simultaneously taken into account by the coupling simulation.In conclusion, the adverse effects from wasting flood resources and the inappropriate flood protection measures which are brought by too large or too small calculation results have been reduced. In engineering practice, for complex river network region, it is recommended to apply the coupling model in calculation in order to improve simulation accuracy.