Structure and electronic properties of silicon carbide nanotube(SiCNT) with and without adsorption of NO₂ are calculated with CASTEP package based on density functional theory.A stable adsorption between nanotube and gas molecule is formed and conductivity of the SiCNT is improved obviously.It is shown that SiCNT is a potential candidate for gas sensors.It is expected to provide a useful guidance in developing SiCNT-based sensors for NO₂ molecules.