Abstract: In order to acquire the input conditions of super-cavitaion vehicle control trajectory and overall design, a scaled model experiment on tail rudder was carried out to investigate the generation of ventilated supercavity and the dynamics characteristics of tail rudder angle of an underwater vehicle. The effects of ventilation air amount and tail rudder angle upon the configuration and hydrodynamics characteristics of a model supercavity were analyzed to obtain the influence regularities of tail rudder angle on lift force and angle of attack (AOA) and ventilation air amount on tail rudder efficiency. In addition, compensation measures for the supercavity tail floating-up caused by gravity were discussed. The experiment results show that in a wet state, the lift curve slope of tail rudder surfaces of an underwater super-cavitaion vehicle is a positive constant to be projected to the global area as the same as a common underwater vehicle under the same condition; when the super-cavitaion occurs and the AOA is 0.4°, the rudder effect will be reduced because of coupling lift force loss of main cavity, and it is insensitive to ventilation air amount; when the AOA is bigger than 1.2°, the characteristics of the rudder effect will be gradually restored, at the moment the main cavity has been away from the wing and the rudder surfaces are in a wet state.