The invention provides an asymmetric structure of an external hanging supporting system of a large movable arm tower crane. A horizontal supporting beam is used for bearing a two-beam-combined C-shaped frame, an inclined pull rod embedded part and an inclined supporting rod embedded part are vertically arranged in the vertical direction and are embedded in a first building structure and a second building structure correspondingly, the two ends of a vertical inclined pull rod are connected with the inclined pull rod embedded part and the first end of the horizontal supporting beam correspondingly, the two ends of a vertical inclined supporting rod are connected with an inclined supporting rod embedded part and the first end, and the vertical inclined pull rod and the vertical inclined supporting rod form a splayed shape rotating by 90 degrees clockwise, and the vertical inclined pull rod is arranged on the upper portion; a horizontal inclined supporting rod embedded part is used for being embedded in a third building structure, and the two ends of a horizontal inclined supporting rod are connected with the horizontal inclined supporting rod embedded part and the second end of the horizontal supporting beam. The problem that an attaching point needed by the tower crane is obstructed by a shrinking or non-shrinking wall is solved, the clear force transmission is ensured, welding deformation is reduced, welding quality is ensured, design is ingenious, the structure is simple, use is easy and convenient, and the structure is suitable for being applied and popularized in a large-scale manner.