Inspired by recent successes in the development of graphene-based gas sensors capable of single gas molecule detection, we investigate the adsorption of gas molecules (NO, NO2, NH3, CO, SO2 and H2S) on gamma-graphyne which has an energy gap of 0.49 eV via first-principle calculations. The results show that the adsorption of NO (or NO2) at an adsorption density of above 2% (or 4%) can change the graphyne from semiconductor to semimetal or metal, while the other molecules have little effect on the energy gap, suggesting that gamma-graphyne can be used as sensitive sensor for selectively detecting NO2 or NO molecules. (C) 2017 Elsevier B.V. All rights reserved.