Method for producing large-diameter steel tube by using two blocks of arc panels with unequal wall thickness

Provided is a method for producing a large-diameter steel tube by using two blocks of arc panels with unequal wall thickness. A steel tube body is composed of two blocks of arc panels with unequal wall thickness, lofting and cutting are conducted on the basis of the arc central lines of the two blocks of steel panels, preparatory cutting is conducted on a straight panel thin steel plate and a straight panel thick steel plate, the straight panel sheet plate and the straight panel thick steel plate are full penetrated and welded into a block of whole straight panel, pre-pressing arc treatment is conducted, circular tube rolling is conducted from the end head position of the thin steel plate by using a three-roller plate coiler, arc formation on the position where the thin steel plate is in butt joint with the thick steel plate is gradually achieved, and arc rolling of the thick steel plate is continued till completed to enable the spliced whole straight panel to form a circular tube with to-be-welded openings;