Abstract: To improve the sealing performance of aero-engine labyrinth seals, a sine bush structure was proposed based on the smooth bush configuration. Numerical simulation schemes are designed by means of orthogonal experimental design. The influences of structural parameters including the depth, cavity quantity and relative position of cavities of the sine bush on the leakage characteristics of labyrinth seals are systematically explored. Combined with the results of range analysis and variance analysis, the optimal configuration of the sine labyrinth bush was obtained. The results indicate that among the three influencing factors, the cavity quantity of the bush has the most significant effect on leakage amount, followed by bush depth and relative position of cavities. Compared with the smooth bush, the leakage amount is reduced by 43.3% when the depth is 0.7 mm, drops by 54.6% with 24 cavities, and decreases by 33.3% as the cavities shift rightward by 0.125 mm. Within the research scope, the optimal configuration of the sine bush is determined as bush depth of 0.3 mm, 24 cavities, and a rightward cavity offset of 0.125 mm. The leakage amount of the sine bush increases linearly with the rising pressure ratio. At the pressure ratio of 1.1, its leakage amount is 52.3% lower than that of the smooth bush. The growth rate of leakage amount decreases obviously under high pressure ratios. When the pressure ratio rises from 1.7 to 2.1, the sine bush induces multi-scale vortices, strengthens energy dissipation and flow separation, and effectively restrains leakage under high pressure ratio working conditions. In this process, the leakage amount only increases by 6.9%.