The gas sensing properties of (8,0) SWCNT on which a Co atom substitutes one carbon atom towards four types of SF6 decomposed components (SO2, SOF2, SO2F2, H2S) are investigated using density functional theory calculations. The adsorption structures, adsorption energies, charge transfers, magnetic moments, valence electron occupations, band structures and density of states (DOS) have been discussed. The results are as follows: (1) All adsorptions are exothermic processes with little structural deformation of SO2 and H2S gas molecule while comparatively obvious bond ruptures are taken place towards SOF2 and SO2F2. Co-SWCNT loses electrons when interacting with SO2, SOF2 or SO2F2 but serves as an electron acceptor to H2S. (2) The adsorption of SO2 or SOF2 introduces a great degree of magnetism transfer from Co-SWCNT to gas molecule while the magnetism is still mainly concentrated in Co-SWCNT after SO2F2 or H2S adsorption. (3) Valence electron occupation changes at different levels with different gas molecule adsorption and electron transfer between Co's own orbitals is observed. (4) The adsorptions of four kinds of gas molecule have different influences on band structures and density of states. The introduction of SO2, SOF2 or SO2F2 increases the bandgap in various degrees. The results of DOS are in good accordance with the above results and band structures. (C) 2017 Elsevier B.V. All rights reserved.