Based on the empirical formula,the leakage of square labyrinth seal was calculated by using the flow field analysis software FLUENT.The influence of shaft speed,clearance,cavity depth and cavity width on the leakage of square labyrinth seal was analyzed.The performances of circular labyrinth seal and diamond labyrinth seal were also analyzed.The above analysis structures were applied to the labyrinth seal of the gear box of highspeed train.The results show that the leakage of square labyrinth seal is increased with the increasing of gap width,and decreased with the increasing of shaft speed,cavity depth and cavity width.The leakage is reduced for the circular seal by increasing the radius of the seal cavity and the diamond seal by increasing the included angle.Among of the square,circular,diamondshaped labyrinth seals with the same crosssectional area,the circular cavity labyrinth seal has the smallest leakage under the same conditions.The labyrinth seal of the highspeed train gear box was optimized according to the analysis results,and the leakage of the labyrinth seal is reduced.