The thin polycrystal Cr2O3 films were synthesized by RF - magnetron sputtering with followed annealing at T = 673 K in an air atmosphere. The grains diameter in the thin Cr2O3 film is 40–70 nm, Eg = 3.3±0.2 eV. In the temperature range of 303–473 K, the Cr2O3 films show high response to NO2, Н2, vapors of acetone and toluene, weakly react to CH4 and CO and have the relatively weak dependence of resistance on humidity. The qualitative model of the gases influences on the thin Cr2O3 films electrical properties was proposed.