The invention relates to a vacuum-energy-storage-type launching catapult for a fixed-wing aircraft. The vacuum-energy-storage-type launching catapult is formed through sequentially connecting an electric winch, a trailer wagon, a speed transformation, a cable winding pulley, a large-diameter piston, a large-caliber vacuum cylinder, an oil pump, an oil storage tank and the like. The electric winch draws the piston to slowly rise to an upper dead point from a lower dead point under the deceleration of the speed transformation, so as to enable the interior of the vacuum cylinder to reach a completely-vacuum state and complete energy storage; the piston enables the trailer wagon to drive the aircraft to rapidly advance and launch through the acceleration of the speed transformation under the propulsion of atmospheric pressure and self-gravity, so as to complete catapult. Data related to specific embodiments of the invention are as follows: the catapult traction distance is 99 meters, the constant net traction force is 31.4 tons, the energy storage power is 600kw, the energy storage time is 60 seconds, the minimum requirements of a power supply on power is 800kw, the power consumption for catapult of one aircraft is lower than 20 kilowatt-hours, the gross weight of the catapult is lighter than 60 tons, and a system main body, i.e., the large-caliber vacuum cylinder has the height of 126 meters and the volume of 465 cubic meters. The vacuum-energy-storage-type launching catapult has the most principal features of uniformity in acceleration, little heat generation, low energy consumption, electrification, light weight and few systems.