Abstract: To reveal the leakage and rotor dynamic characteristics of brush seal under high inlet preswirl condition, the whirling rotor method and the nonlinear Darcian porous medium model were used to establish the numerical analysis model of the brush seal. Under the condition of high preswirl condition（preswirl ratio λ＞0.8）, the influence of pressure ratio and rotor spinning speed on the leakage and rotor dynamic characteristics of the brush seal was analyzed, compared with the condition of low inlet preswirl. The leakage and rotor dynamic characteristics of the brush seal were numerically calculated under five pressure ratios（2.0, 3.0, 3.5, 4.5, 5.5） and five rotor spinning speeds（3 000, 6 000, 7 500, 9 000, 12 000 r/min）. The results show that the leakage of brush seal under high inlet preswirl condition is slightly less than that under low inlet preswirl condition. The direct stiffness and cross-coupled stiffness of the brush seals under high inlet preswirl condition are both greater than those under low inlet preswirl condition, and increase with the pressure ratio. The cross-coupled stiffness under high inlet preswirl condition is always a huge positive value. The influence of rotor spinning speed on the direct stiffness of the brush seals is small under low inlet preswirl condition, while the direct stiffness of brush seals decreases slightly with the increase of rotor spinning speed under high inlet preswirl condition. With the increase of rotor spinning speed, the increase of cross-coupled stiffness under high inlet preswirl condition is significantly greater than that under low inlet preswirl condition, which results in a significant decrease of effective damping.