The invention discloses an upper-air formwork support and outer scaffold shared cantilever structure, and belongs to the technical field of buildings. The upper-air formwork support and outer scaffoldshared cantilever structure comprises cantilever steel beams, a horizontal rectangular steel plate, a U-shaped pull ring and the like. The cantilever steel beams comprise a first cantilever steel beam and a second cantilever steel beam, the first cantilever steel beam is in lap joint to a floor, the lap-joint end of the first cantilever steel beam and the floor is connected through the U-shaped pull ring, the horizontal rectangular steel plate is mounted on the bottoms of the first cantilever steel beam and the second cantilever steel beam, the second cantilever steel beam is connected with the side of the floor, and rectangular hollow braces and triangular steel plate are mounted between the lower portion of the horizontal rectangular steel plate at the bottoms and the side wall of the floor. Through the structure system, the horizontal rectangular steel plate is mounted, the first cantilever steel beam and the second cantilever steel beam are better stressed, it is ensured that a formwork support and an outer scaffold are erected at the same time, bearing capacity is high, all cantilever steel beams adopt brace types, a traditional single steel wire rope is not adopted for inclined bracing, the stability of the cantilever steel beams is improved, and stability and safety of a cantilever scaffold can be improved.