The detection of triethylamine gas is of great importance to human health, the environment and food safety. In this paper, a simple and economical hydrothermal method for the synthesis of Mo-SnO2 composites is proposed. The structure and morphology were characterized in detail by XRD, TEM, SEM, etc. The effects of different proportions of Mo on SnO2 were studied and the results show that SnO2 in 5%Mo-SnO2 nanomaterials has small grain size. The gas-sensitive properties of Mo-SnO2 samples to triethylamine gas were systematically tested. The results show that the 5%Mo-SnO2 nanomaterials have great gas-sensitive properties. It has not only fast response and recovery time (Tres/Trec=15 s/25 s) but also good selectivity and reproducibility for 100 ppm triethylamine gas at an optimum operating temperature of 250 °C. Triethylamine gas can also be detected at a minimum concentration of 375 ppb. Therefore, the 5%Mo-SnO2 nanomaterials synthesized in this experiment have some prospects for application in the field of triethylamine gas detection.