Ship-propeller-rudder interaction affects the overall performance of the ship. For twin-propeller ships which equipped with twin-rudder, the variation of rudder angle will aggravate the interaction of rudder & propeller & ship and have a significant influence on the overall ship performance. Based on the experimental method, both the resistance and self-propulsion performance of a twin-propeller ship which equipped with twin-rudder at different symmetrical rudder angles near the design speed are studied regarding the ITTC recommended guidelines for resistance tests and self-propulsion tests, and the optimal rudder angle at the inflection point is considered. For the resistance test, the total ship resistance at the rudder angle of 0, 2, 4, 6 and 8 degrees is studied, and the optimal rudder angle is 6 degree. For the self-propulsion test, the ship’s self-propulsion performance at the rudder angle of 0, 2, 4 and 6 degrees is studied, and the best rudder angle is 4 degree. And the optimal rudder angle is similar at different speeds. Therefore, the symmetrical rudder angle has a significant effect on the resistance and self-propulsion performance of a twin-propeller ship which equipped with twin-rudder, and the optimal rudder angle can effectively reduce the energy consumption of the twin rudder type of ship.