Abstract: The spillway dam is a complex three-dimensional structure system formed by different types of structure. In practice, some structural damage may even result in an accident for the whole project. The flow pattern and hydrodynamic load acting on structures are studied through the hydraulic model test. By means of experimental modal analysis technique, dynamic characteristics for each structures are obtained. In order to study flow-induced vibrations, the multisimilarity model for the complex structure is made which satisfies simultaneously hydrodynamic, concrete and metal structure vibrations, and mutual interaction of fluid and structure as well as structures each other.