The invention discloses an installation method for a steel skeleton of a large steel structure factory building, belonging to the technical field of installation of metallurgy steel structure factory buildings. The invention provides an installation method for a steel skeleton of a large steel structure factory building, which is low in installation cost, convenient for installation operation, efficient and safe. In the installation method, firstly, the steel skeleton is centered, the bottom section sectional steel column is fixed, then, a temporary operation platform and an auxiliary device for assembly, which are convenient for the installation operation, are mounted at the tops of the centered and fixed bottom section sectional steel columns of each lattice, thus, safety, efficiency and convenience in the installation operation can be guaranteed, meanwhile, since each steel column is divided into two sections, or three sections, even more sections for installation, the hoisting device can be a medium scale device with smaller hoisting capacity, thus, installation cost of the hoisting device can be reduced greatly.