The invention relates to the technical field of combined steel truss installation construction, in particular to a narrow-space long-span multi-surface special-shaped combined steel truss installationconstruction method. The method is characterized in that a BIM technology is utilized to optimize arcs and establish a high-level control network, and field data is finely adjusted in combination with a computer; during field construction, steel truss segments are spliced, full hall scaffold operation platforms and supporting frames are erected at building structure ends and steel truss connection parts synchronously, and a main truss is formed through assembling and welding; and then sliding units are formed through connection of secondary trusses among main trusses, and existing concrete linking beams are utilized to arrange sliding tracks, and in-place sliding is performed according to a structure accumulating sliding mode. Through the method, the quantity of scaffolds in use can be greatly reduced, the method is safe and reliable, most overhead work is reduced, construction is convenient, a machine used for lifting is relatively small, and mechanical cost is low. The method is mainly applied to the technical field of combined steel truss installation construction.