The metal oxide semiconductor material molybdenum oxide (alpha-MoO3) is one of the current research hotspots for gas-sensitive materials. Studies have shown that the current gas-sensitive sensor elements of pure phase alpha-MoO3 materials still have disadvantages: they operate at high temperatures, are unstable, and take a long time to respond. To improve the above mentioned drawbacks, SnO2-Bi/MoO3 composites for ethanol gas sensors were synthesized in this paper by a simple hydrothermal method and liquid phase chemical method. The surface of Bi/ MoO3 composites was uniformly covered with SnO2 nanoparticles to enhance their specific surface area. The Bi/ MoO3 nanoribbons functioned as channels for electron transfer, creating a linkage among the SnO2 nanoparticles. At 300 degrees C, the SnO2-Bi/MoO3 (wt%: 15 %) responded to 100 ppm ethanol was up to 26.39. The measured value was approximately 3.93 times higher compared to MoO3 (response = 6.72, temperature = 300 degrees C) and 2.20 times greater than Bi/MoO3 (12.01). In addition, the heterojunction materials of SnO2-Bi/MoO3 (wt%: 15 %) respond quickly, are selective, and stable among these composites. The mechanism of gas sensing was thoroughly examined with respect to the ability of carrier transfer, the synergistic interaction between SnO2 and MoO3, the effects of heterojunctions, and improvements in morphology. Here, a sensor utilizing a ternary nanocomposite comprising SnO2-Bi/MoO3 is reported, and its enhanced sensing performance highlights the fact that the SnO2Bi/MoO3 material has a narrow bandgap, abundant surface vacancies and highly active sites. A straightforward approach is presented for creating MOS-based nanocomposites aimed at the efficient identification of ethanol.