OFT calculations are performed to investigate the healing process of C-vacancy defective silicon carbide nanotubes (SiCNTs) by CO molecules. The healing process consists of the CO-vacancy recombination, followed by extra O removal by another CO molecule. It is found that the removal of the extra O atom on SiCNTs is the rate-limiting step, for which the energy barrier decreases with an increase of tube diameter. Nevertheless, the healing of SiCNTs is nearly independent on the tube chirality. Our results can be useful not only in the purification of SiCNTs, as well as in the removal of CO gas. (C) 2017 Elsevier B.V. All rights reserved.