Manufacturing method of large thin-wall metal box body

The invention relates to a manufacturing method of a large thin-wall metal box body. The manufacturing method comprises the following steps that a first body and a second body are assembled and welded; the first body and the second body are supported on the two opposite sides of the supporting core mold; side wall structures are fixed to the two opposite sides of the first body and the second body in a sealed mode, so that the first body and the second body define a square frame through the side wall structures on the two sides; the whole square frame body is subjected to stress relief; and the supporting core mold is taken out, an external connector of the square frame is machined, and manufacturing of the box is completed. The first body and the second body are firstly assembled and welded, the manufacturing efficiency can be improved, the first body and the second body are supported through the supporting core mold, and then the side wall structures on the two sides of the square frame body are installed,