Self-doped nanocolumnar vanadium oxides (SNVO) thin film is fabricated by glancing angle deposition without any nanotemplates and additives. SNVO sensor shows a high selectivity to NO2 at low temperature due to a porous nanostructure with narrow necks and a catalytic effect of residual VO2. The residual VO2 acts as an intrinsic electron donor by pseudo-free electron, which helps adsorption of oxygen ions and extends the depletion region.