To know the sealing performance of an improved brush seal on turbine, the leakage flow characteristics and distribution on rotor surface, bristle pack free height and fence height were numerically analyzed by adopting a non-Darcian porous medium model. And a corresponding comparison between labyrinth seal and brush seal was performed. The analysis shows that at the same clearance and pressure ratio the flow fields in hybrid brush seal are more complex than that in labyrinth seal and the leakage rate of brush seal is significantly less than that of labyrinth seal, at the same structure and parameters the leakage rate increase with the rise in pressure ratio. More over, the axial static pressure and turbulent kinetic energy of rotor surface gradually decline with a ladder-like distribution from inlet to outlet, the racial static pressure of fence height tends to be constant values. The radial velocity and turbulent kinetic energy increase with the rise in pressure ratio. The lower parts of the bristle and the fence height have obvious effect on the leakage characteristics. The results provide theoretical basis for the design of brush seal structure and the improvement of performance.