Abstract: The drum labyrinth is an important sealing structure of aeroengine fan or compressor and the sealing performance of drum labyrinth greatly affects the overall performance of aeroengine. In order to fully understand the cavity pressure distribution of the drum labyrinth seal structure and its sealing mechanism, the flow of drum labyrinth seal has been numerically investigated with numerical method and the effect of rotating speed and outlet static pressure of labyrinth seal on static pressure of the drum are emphatically discussed. The simulation results show that 1) the static pressure of the drum generally decreases first and then increases along the flow direction; 2) compared with the variation of rotating speed, the effect of the outlet static pressure of labyrinth seal on static pressure of the drum is more significant; 3) under a certain rotating speed, static pressure of the drum increases linearly with the increasing of the outlet static pressure of labyrinth seal.