Transition header of ultra-supercritical boiler unit

The invention discloses a transition header of an ultra-supercritical boiler unit, and belongs to the technical field of boilers. The transition header of the ultra-supercritical boiler unit comprisesfirst small header pipe joints, a high-temperature heating surface steam outlet small header, a second small header pipe joint, a first transition header pipe joint, a transition header body, a second transition header pipe joint, a big header pipe joint and a last-stage reheater outlet big header; one set of first small header pipe joints are evenly welded to the lower end of a body of the high-temperature heating surface steam outlet small header; the high-temperature heating surface steam outlet small header communicates with the transition header body through the second small header pipejoint and the first transition header pipe joint; and the transition header body communicates with the last-stage reheater outlet big header through the second transition header pipe joint and the bigheader pipe joint. Respect