Provided is a panel enclosing structure for an air-separation cold box. The air-separation cold box is mainly composed of surrounding truss structures and cold box panels enclosing the surrounding truss structures, and each truss structure is composed of long cold box columns on the two sides, multiple cold box cross beams and two inclined struts, wherein the cold box cross beams are sequentially fixed to the cold box columns on the two sides in an up-and-down mode, the two inclined struts are sequentially fixed to the upper cold box cross beam, the middle cold box cross beam and the lower cold box cross beam in a crossed mode from top to bottom, and the middle of the middle cold box cross beam serves as a cross point of the two inclined struts; the truss structures are vertically fixed to the cold box cross beams, and multiple stiffening ribs which extend to the top from the bottom are horizontally and evenly distributed on the cold box cross beams. Cold box panels used for wrapping the whole cold box are welded to each truss structure in a sealed mode; according to connection between the cold box panels and the cold box columns and the cold box cross beams, the overlapping length, reserved on the outer side faces of the cold box columns and the cold box cross beams, of the cold box panels is 30 mm or above, 4-cm fillet weld all-around welding, namely sealing welding is adopted at outer overlapping joints for avoiding air leakage, and 4-cm fillet weld intermittent welding is adopted at inner overlapping joints.