The invention belongs to the technical field of installing construction of large-span steel tube truss protective sheds in building installation engineering and particularly relates to a rapid-construction method used for overall installation of a large-span steel truss. By the adoption of the method, a temporary support or a full support is prevented from being erected inside an existing line, and basic construction time and key point operation time inside the existing line are shortened. The method includes the detailed construction steps that 1, steel stand columns are installed; 2, the truss is pre-pressed; 3, the truss is spliced on site; 4, a space truss is integrally hoisted; 5, secondary truss bodies between sets are hoisted; 6, other truss bodies are hoisted. The method has the advantages that the construction technology is simple, practical value is high, the using effect is good, technical requirements of related specifications are met, construction quality is guaranteed, construction efficiency is improved, operation time inside the existing line is shortened, interference caused by a traveling crane inside the existing line is reduced, safety risks are reduced, the construction period is shortened, the construction cost is lowered, and good economic benefits are achieved.