The invention relates to a takeoff device and method of a carrier-borne aircraft of an aircraft carrier. The takeoff device comprises a single-pendulum catapult mechanism which is arranged at the side edge of the aircraft carrier and used for catapulting the carrier-borne aircraft, wherein a swinging arm is arranged in the mechanism, the lower end of the swinging arm is connected with a catapult which can be movably connected with the aircraft carrier, and the catapult is provided with a booster engine; the upper end of the swinging arm is of a single-pendulum suspended structure which is a rotating shaft formed by the outer end of a cantilever extending out of a aircraft carrier body and the upper end of the swinging arm, the rotating shaft can be provided with a swinging assisting device, and the vertical swinging plane of the swinging assisting device is parallel to the side of the aircraft carrier and vertical to the cantilever; and a platform used for settling the carrier-borne aircraft till takeoff is arranged at one side of the single-pendulum catapult mechanism at a certain height. Before takeoff, the catapult is settled besides the platform and movably connected with the carrier-borne aircraft; during the takeoff, the settle is canceled, the catapult and the carrier-borne aircraft do single-pendulum movement instantly, and together with an engine and/or the force of the swinging assistant device, the carrier-borne aircraft is swung to the opposite side in an acceleration way, so the carrier-borne aircraft is catapulted and the takeoff is completed. The invention has simple structure as well as low fabrication and use cost and is suitable for the takeoff of various carrier-borne aircrafts of aircraft carriers.