Abstract: A full three-dimensional model was set up for a labyrinth seal, in which the flow field was calculated and analyzed under different working conditions using commercial CFD software Fluent, so as to study the relations of the fluid-induced force with the rotational speed, pressure ratio and the eccentricity, etc., and to obtain the dynamic coefficient and whirl coefficient of the seal that may influence the stability of the rotor. Results show that with the rise of rotational speed, pressure ratio and eccentricity, the whirl coefficient increases accordingly, and the stability of the rotor is hence reduced.