Abstract: The structure and working modes of a kind of flexible dam are described in this paper. A general expression for unit width buoyancy is given according to mechanic analysis and the principle of moment balance. Based on the prototype of riverbed terrain and current conditions around Xiaoshan Hanzhou bay delivery wharf in the Qiantang River， an undistorted flume model having a scale of 1:40 is established. The experiment results show that the tension at the bottom of the flexible dam is directly related with the size of the buoy and the ratio of the dam length and water depth. At the same time， the incipient velocity of the sandbag blanket and sandbag bundle used to anchor the flexible dam, and the size and quantity of sandbags needed to keep the anchorage system stable are obtained. The experiment results of the integral stability of the dam indicate that： the flexible dam with appropriate buoy, height and anchorage system can play a role in flexibility, suspension, movability and diversion， and can keep itself stable in some flow conditions. As a new engineering measure， there are quite a few studies on its theory and experiment. By comparison with the solid dam， the flexible dam has smaller negative influence， so the study in this paper has an important academic significance and can be used as a reference for similar works. For this new river engineering structure, it is still necessary to further study and improve it in the engineering practice.