Abstract: Considering the rudder features of a twin-propeller and twin-rudder ship, a series of numerical simulations of rudder-force tests with different rudder sectional parameters are carried out by using the Computational Fluid Dynamics method, from which the normal force coefficients of the rudder are obtained and the effects of rudder aspect ratio and thickness ratio on the hydrodynamic performances of the rudder are analyzed. On this basis, the standard turning circle and zigzag maneuvering motions are numerically simulated with the established mathematical model of ship maneuvering motion with four degrees of freedom. The maneuvering parameters are obtained from numerical simulations and the effects of rudder aspect ratio and thickness ratio on the turning ability, course-keeping ability and yaw-checking ability of the twin-propeller and twin-rudder ship are discussed. The research findings provide reference significance for optimizing rudder geometric parameter design and improving ship maneuverability.