The Large Eddy Simulation (LES) method was used to study the interaction between propeller wake and a rudder. The INSEAN E779A propeller and the NACA0020 rudder were used, and the method was employed to analyse the vortices. The evolution of the propeller-wake in oblique flows and the effect of oblique flows on the propeller wake vortex were studied. The pulsating pressures on the rudder surface for different oblique-flow angles were compared. The results show that the hydrodynamic coefficients of the propeller and the rudder increased under oblique flows. The vortex of the propeller shifted as the angle changed, but it did not completely coincide with the oblique-flow angle. Under the effects of the propeller-wake, the rudder surface generated a pulsating pressure. The frequency of this pulsating pressure relates to the blade frequency of the propeller, and the amplitude of the pulsating pressure increased with the oblique-flow angle.