Triethylamine is a kind of volatile organic compound, which is flammable and toxic. Here, PdRu alloy nanoparticles (NPs) were used for modifying SnO2 to make it more selective for triethylamine. Monodisperse PdRu alloy NPs were produced through coreduction in polyol solution, while the SnO2 nanoparticles with a small particle size were generated by a hydrothermal method. The sensor based on 0.5 wt% PdRu-SnO2 exhibited a high response (S = 256) to 100 ppm triethylamine when the temperature was 220 °C. The response was 12 times more than trimethylamine and 10 times higher than that to NH3. Moreover, it showed rapid response speed (2 s) to triethylamine. SnO2 with small particle size had many acid sites, which showed selective detection of triethylamine due to acid-base reaction. Besides, the catalytic property of PdRu NPs also played a role in improving performance. This work provides a new method for the fast identification of triethylamine in chemical industry plant.