Abstract: To solve the general oil mist pollution in thrust bearings of large hydro-generator units, based on the theory that dredging can obtain better effect than blocking, a new centrifugal gas seal structure was proposed, which was verified in one unit of Xiluodu Hydropower Station. In this structure, centrifugal blades were installed on the main shaft of the unit, and it could turn round with the shaft to generate high speed and high pressure airflow in the entire flow channel. The spilled oil mist will be brought into the volute channel by the airflow above and be absorbed by the oil mist system finally. So the oil mist was prevented from being sucked away by the negative pressure under the rotor hub arm and oil pollution was effectively controlled. In addition, the CFD software was used to conduct three-dimensional numerical simulation on the internal flow field of the centrifugal air seal. The aerodynamic performance of the blades and the internal flow field law were discussed. The simulation results were consistent with the experiment data, which verified the reliability of numerical simulation method. The research results can provide a new solution for bearing oil mist control of large hydro-generator units, and a reference for the research and optimization of gas seals.