The invention provides a method for installing an overhead steel structure high, which belongs to a method for constructing a fixed structure. The prior installation method has defects that precise positioning is hard to realize and installation precision is hard to guarantee. The method comprises the following steps of: accurately modeling and correctly lofting and cutting, correctly paying off and accurately positioning; installing embedded parts, a temporary assembly jig and an upright post according to the paying-off position; positioning and fixing a joint on the temporary assembly jig; orderly lifting a main girder, a secondary girder and a purline; and unloading and dismounting the temporary assembly jig. The method is easy to guarantee manufacture precision of each component and installation precisions of the embedded parts, the temporary assembly jig, and the joint; the on-site lofting and cutting is unnecessary to undergo, and the on-site lifting and connection (welding) of each component are convenient.