When a composite nanostructure is fabricated through van der Waals interaction only, the interaction among components may be sensitive to environmental conditions. To endow such a structure with relative stability, new covalent bonds should be applied. In this paper, a welding method for welding a circular graphene with a defect gap through a moving fullerene (C240 or C540 buckyball) is presented. When the buckyball moves above the gap, the two faces of the gap are attracted to each other and the distance between the two faces is shortened. When the dangling carbon atoms on both faces of the gap are excited to form new normal sp(2)-sp(2) carbon bonds, the gap can be sewn up quickly. Molecular dynamics simulations are presented to demonstrate the welding process. When the gap is a sector, an ideal cone can be fabricated using the present method. (C) 2016 Elsevier B.V. All rights reserved.