The invention provides an externally-mounted work platform for a fabricated building. The externally-mounted work platform for the fabricated building comprises one or two or more work platform units which are horizontally arranged on the outer side of a prefabricated side
fascia, multiple fastening devices which are pre-buried in the prefabricated side
fascia, and multiple hook bases which are fixedly connected with the corresponding fastening devices through fastening pieces, wherein each work platform unit comprises a one-layer or two-layer or three-layer or multi-layer framework which is formed by hollow profiles through
welding, protective screen or guardrails arranged on the outer sides of all
layers of the framework and protective screens or pedals which are arranged on the bottoms of all
layers of the framework, and the work platform units are hooked into the hook bases through the hollow profiles transversely arranged on the inner side of the framework to be fixedly arranged on the outer side of the prefabricated side
fascia. According to the externally-mounted work platform for the fabricated building, safe and reliable
work space is provided for workers for outer wall construction, construction is facilitated, the construction efficiency is improved, construction cost is reduced, objects falling from high altitudes and casualties are prevented, the structure is simple, the weight is low, and multiple functions are achieved. The invention further provides a method for operating the externally-mounted work platform.