A series of In₂O₃-WO₃heterojunction nanofibers were synthesized via the electrospinning technique in this study. The morphological and microstructural properties of these nanofibers have been characterized by XRD (X-ray diffraction), field emission scanning electron microscopy (FESEM), selected area electron diffractive (SAED), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The gas sensing properties of the In₂O₃-WO₃heterojunction nanofibers were evaluated. The results indicate that the sensor based on In₂O₃-WO₃nanofibers, in which the molar ratio of In₂O₃-WO₃is 1.5:100, exhibits the largest response toward 50 ppm acetone among those nanofibers, having a response about 12.9-50 ppm acetone, which is almost 2.5 times higher than that of sensor based on pure WO₃nanofibers at the optimum operating temperature. What's more, the sensor can detect acetone in sub-ppm concentrations with high response, the limit of detection (LOD) of the sensor based on heterojunction nanofibers is similar to 0.4 ppm, which is promising for being used in noninvasive detection of illnesses.