The invention relates to a construction method for an upper cylinder of a
cooling tower of a steel structure. The method comprises the steps that 1, a triangular frame which is enclosed by a cross beam and inclined beams is manufactured; 2, upper and lower locking plates are arranged on the intersections of the two ends of the cross beam and the two inclined beams respectively, and through holes are formed in the upper and lower locking plates; 3, the triangular frame which passes inspection is conveyed to a cavity which is defined by cone segments; 4, a
tower crane is used for reversely hoisting the to-be-installed triangular frame to the installation position, it is guaranteed that a lower blocking plate of the bottom of the to-be-installed triangular frame is flush with the upper
locking plate on the cross beam of an installed triangular frame, back levers penetrate through the through holes of the upper and lower locking plates, and wedges are put into the through holes; 5, the wedges are hammered, and the outer surface of the triangular frame is flush; 6, the perpendicularity of the triangular frame is adjusted by using an increase line; 7, the triangular frame is fixed and welded by using point
welding; 8, the fourth to seventh steps are repeated, and other triangular frames at the same layer are installed on the circumference; 9, the fourth to eighth steps are repeated,and the other
layers of triangular frames are installed. According to the construction method, the construction efficiency is high, installation and positioning are reliable, and the technical problemis solved that a cylinder with the large
diameter is difficultly constructed.