The invention relates to a segmental slipping and assembling process of an overhead large-span steel structure, which is characterized by comprising the following steps of: firstly building a temporary track beam support, then arranging a slipping track beam and an assembling jig frame on the temporary track beam support, assembling a steel structure truss element on the jig frame according to drawing requirements, dismantling the assembling jig frame after the assembly is finished, pushing and slipping the steel structure truss element forwards along the a slipping track, moving the steel structure truss element to the expected position of the steel structure, then carrying out next span area steel structure truss element assembly on the emptied-out assembling jig frame, carrying out welding connection between the next span steel structure truss element and the previous element, slipping and pushing the steel structure truss elements to the expected position in sequence, analogizing the process in sequence till all steel structure slipping and assembly are finished, and finally unloading, landing and fixing to finish the whole installation work of the steel structure.