Brush seals are widely used in industry because of their excellent contact and flexible sealing. This paper investigates the influence of the axial width of the pressure relief chamber and the bristle diameter on the leakage characteristics of brush seals. Rotor speed cycle tests are conducted using low-hysteresis brush seals, and the rotor's centrifugal expansion and recovery process is simulated by increasing and decreasing the rotor diameter in the static state. The results show that the low-hysteresis structure has better sealing performance than the conventional brush seal, and the optimal axial width of the pressure relief chamber is 0.4 mm. This structure gives the smallest leakage amount. The leakage coefficient of the low-hysteresis structure with a bristle diameter of 0.13 mm is about 37% higher than that with a bristle diameter of 0.08 mm over the entire test speed range and exhibits stronger hysteresis effects. The results of this paper can be used as a reference for the design of brush seals for engineering applications.