Abstract: CFRD built on deep alluvium deposit has the advantages of simplified cofferdam， shortened construction period and less investment. These types of dams are built with complex seepage prevention systems， and the key problem is to control the stress and deformation of the seepage prevention system of the dam. Thanks to accumulating of engineering experience and developing of technique studies， there have been built many CFRDs such as Nalan， Chahanwusu， Jiudianxia， Miaojiaba and so on on deep alluvium deposit， and many dams are going to be built on the same deposit. The behavior of the stress strain of the seepage prevention system is related to the bearing capacity of the alluvium deposit and the design of the seepage prevention system obviously. Based on the engineering information and research results， this paper has summarized the foundation conditions and the seepage prevention system of those concrete faced rockfill dams built or to be built on the deep alluvium deposit. It can be used for reference in designing similar projects, and can provide technique supports for the development of this type of dams. The results show that if the deformation modulus of the alluvium deposit exceeds 40 MPa， the stress and deformation of the seepage prevention system of those CFRD built on the deep alluvium deposit with the height of 100 m to 150 m can be in the permitted range in the future.