Abstract: In this paper， a novel trimaran power transmission device is developed by installing the ordinary ship aft propeller to both sides of the trimaran hull. This novel structure could effectively reduce the noise and vibration of the running propeller and its energy consumption， since the flow field velocity is quite high along the broadside， while the eddy currents and turbulence are practically non-existent. Meanwhile， as the traditional rudder is replaced by the new symmetrical dual-propeller device， the endurance and survivability of the ship is greatly enhanced. Overall， the proposed structure has broad prospects in marine energy saving as well as improving ships' endurance and safety. Moreover， by controlling the duel-propeller with the automobile differential principle， the turning function is easily achieved so that the flexibility and rapidity of the trimaran is also increased.