Abstract: Compared to dikes constructed on the river bed, floating dikes have the advantages over the spur dikes of minor influence to the riverine sediment transport, bed topography, ecosystem and good capability of adaptation to the fluvial conditions. Yet, floating dikes have not been applied to the river regulation, due to the limited understanding of the 3D flow structures around floating dikes. Our experimental studies were conducted to investigate the effects of the floating dike on the 3D flow structures around it. Results showed that after placing the floating dike, the surface water flow deflected into the other side of the flume, and circumfluence occurred right downstream of the dike, where both the vertical turbulent intensity and the absolute value of Reynolds stress were relatively large. Due to impediment effects of the dike, cross-sectional area decreased, causing the increase of flow velocity below and beside the dike and decrease of flow velocity upstream of it. Increase of the immersed depth or the dike length resulted in the increases of flow velocity beside the dike as well as the vertical or lateral scale of the circumfluence, while increasing the dike thickness led to the weakening, or even disappearing of the circumfluence.