The utility model discloses a dynamic display system for a flow tracing line in a water flow. The system comprises a river model, flow tracing line tracer particles, a camera and a digital image processing device; the tracer particles are dispensed into the water flow of the river model; the camera is fixed in a direction perpendicular to the water flow surface of the river model and is used for shooting a movement video of the tracer particles; and the camera is connected with the digital image processing device. According to the utility model, the provided system with a simple structure is easy to construct and can be popularized conveniently. And not only a tracing line can be displayed clearly, but also a changing process of the tracing line can be displayed dynamically, thereby providing a technical support for flood prevention and drought fighting as well as environmental protection and the like.