The invention discloses a steel cylinder final assembly technology. The steel cylinder final assembly technology specifically comprises the following steps: transferring and arranging plate units, marking outer-field inner-mold jig frame and 0-degree position lines, arranging an inner-mold jig frame, applying for inspecting the jig frame, transferring and turning over a cylinder wall unit, positioning and fixing a head board unit P01, assembling and welding the cylinder wall unit, lifting out the inner-mold jig frame from a cylinder jig frame, wholly hoisting and shifting the steel cylinder, and shifting the steel cylinder to the front edge of a wharf. The final assembly technology has the advantages that a special assembly jig frame is arranged inside the steel cylinder, the design of the jig frame is reasonable, personnel can conveniently construct up and down, construction precision of the steel cylinder is ensured, the outer side of the steel cylinder uses domestic advanced vertical gas electric welding to perform welding of vertical welding joints among the plate units, so that welding quality is guaranteed, safety of high-altitude operation of the personnel is ensured, shrinkage and deformation of the plate units in the welding process are all within a controllable range, and size precision of the steel cylinder after the steel cylinder is built is ensured; and meanwhile, the technology is facilitates for safe civilization production, and the cost is reduced.