Abstract: A gas-fluid unsteady numerical simulation was conducted for a large-scale floatation column in this study. Based on the simulation results,the flow field feature of cyclonic unit was analyzed and the mineralization characteris- tic was discussed in terms of the slip velocity between gas and fluid phase. Then movement of bubble and particle was measured with two high speed cameras. The collision behavior and 3D motion trajectory were obtained,which agrees well with the numerical simulation results. The main conclusions on cyclonic unit are as follows:both gas and liquid phase moves tangentially inside of cyclonic unit,and the movement above the cone has the tendency of centripetal and upward,while the centrifugal trend exists in the cone inner area. Below the cone,the fluid moves downward spirally. There are obvious axial and radial velocity difference at the same location between gas and liquid. Although the tan- gential velocity looks the same,it presents a high gradient in radial direction. As to the gas holdup,the value remains 10% -13% in the inner area of cone,while lower than 1% below the cone. As an important separation unit,the cy- clonic unit undertakes the separation of tailings and the recovery of middle-size minerals. The mineralization behaves as the combination of “countercurrent collision” in axial and radial directions in the swirling process. The area below the cone does not have the condition of mineralization. Swirling intensity dominates the separation efficiency of cyclonic unit.