To explore the possible way of detecting the poisonous gas SO2, we have investigated the interactions between SO2 molecule and modified (8,0) single-walled carbon nanotubes by using the density functional theory (DFT) method. The adsorption energies, interaction distances, changes of geometric and electronic structures were all analyzed to investigate the sensitivity of variety of models of CNTs with Ni doping, vacancies, and a combination of them toward SO2 molecule. From our investigations, we found that SO2 molecule was more likely to be absorbed on vacancy-defected CNTs with relatively higher adsorption energy and shorter binding distance compared with the perfect CNTs. In addition, after doping Ni atom on the vacancies, the modified CNTs which were not very much sensitivity to SO2 molecule could become much sensitivity to it. In other words, the number of sensitive adsorption sites increased. The partial density of states (PDOS) and the electron concentration of the adsorption systems suggested the strong electrons interaction between SO2 molecule and defected or Ni-doped defected CNTs. Therefore the vacancies and Ni-doped vacancies CNTs had the potential capacities to make the sensors for SO2 molecule detecting. (C) 2015 Elsevier B.V. All rights reserved.