A triethylamine gas sensor with humidity resistant, high selectivity and highly response is designed. Chromium oxide particles were prepared by heating them in a water bath at 80°C. Pt/Cr₂O₃ nanoparticles was obtained by sodium borohydride reduction. The structure morphology of nanoparticles was characterized by some methods. The gas response test results showed that the modification of Pt improved the response value and selectivity of Cr₂O₃ to triethylamine. It was found that Cr₂O₃-2Pt nanoparticles had the best performance, and at the optimum operating temperature of 160°C, its response value reached 200, 68 times that of Cr₂O₃ (S = 2.95). In addition, the modification of Pt maked Cr₂O₃-2Pt nanoparticles have a wide range of humidity applications. The mechanism of gas response is explained by using Schottky barrier and hole accumulation layer model of Pt and Cr₂O₃ contact and energy band theory.