The movement of fine bubbles in a swirling field determines the mass transfer, heat transfer, and reaction performance of the swirl equipment. This study investigated the separation of fine bubbles strengthened by a swirling field in order to achieve higher separation efficiency of the planar cyclone through optimizing the structure of the convection field. The bubble size and gas holdup in the swirling flow field under different working conditions were explored by combining high-speed camera online measurement and computational fluid dynamics(CFD) simulation. The gas holdup and bubble size of each region in the swirl region, as well as the separation efficiency of gas by swirl eccentricity, were observed at different liquid and gas Reynolds numbers, Re_l and Re_g, respectively. Furthermore, the influence of different swirl eccentricities, d_c, was investigated. It found that the highest separation efficiency can be achieved under all working conditions when swirl eccentricity d_c= 5 mm.