Ethanol, as one of the most widely used volatile organic compounds (VOCs), can cause serious harm to the human respiratory system when exposed to low concentrations of ethanol gas for a long time. Here, we successfully prepared MoO3/Ti3C2Tx MXene nanocomposites by a simple hydrothermal synthesis method, realizing the effective monitoring of low-concentration ethanol gas ([email protected] ppm). The specific surface area of MoO3/Ti3C2Tx MXene nanocomposites (61.044 m2/g) is doubled compared with Ti3C2Tx MXene (33.385 m2/g), which provides more reaction centers and active sites for ethanol molecules. Meanwhile, the gas-sensing results revealed that MoO3/Ti3C2Tx MXene nanocomposites show outstanding selectivity and reproducibility, as well as fast response-recovery (10/49 s). Subsequently, the possible sensing mechanism of the composite was further discussed in detail in combination with density functional theory (DFT). This work provides a new sensing design strategy for detecting VOCs at low-temperature.