The invention discloses a roof steel structure. The roof steel structure is divided into common borders of a plurality of relatively independent areas; every two adjacent independent areas are connected with one common border through purlines, and at least the purlines of one independent area is fixedly and slidably connected with the common border through hinge points; and each hinge point comprises a first steel disc and a second steel disc, wherein the first steel disc is welded on the corresponding common border, the second steel disc is welded on the corresponding purline, and the first steel disc and the second steel disc are adjustably fixed through oblong holes. According to the roof steel structure, area-by-area dismounting of a jig frame is achieved by installing common borders and hinge points, and the construction speed of a building is increased.