Simulation of silt dam breach is of great importance to risk assessment and disaster alleviation. Taking Qiugou silt dam in Yanan city as an example, in the small-scale basin with no terrain data, we use UAV scanning technology to obtain the silt dam field situation and use the virtual reality software such as 3ds Max to simulate the collapse of the silt dam. The 3D virtual scene demonstrates the simulation development of dam breach and process of water flow, and the flood submerged range and volume are obtained, which provides technical support for the management and safety of silt dams.