A series of La₂O₃-doped WO₃nanofibers were synthesized by an electrospinning method in this work The structure composition and morphology of nanofibers were 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). Sensors based on these nanofibers were fabricated by hot-press on the ceramic plates. The gas sensing properties of the undoped and La₂O₃-doped WO₃(La3+ :W6+ = 1 mol%, 3 mol% and 5 mol%) nanofibers were tested to various gases. The sensors based on La₂O₃-doped WO₃nanofibers, in which the molar ratio of La3+:W6+ is 3:100, exhibit highest response toward 100 ppm acetone, having a response about 12.7, which is almost 2 times higher than that of sensor based on pure WO₃nanofibers. These results indicate that the acetone sensors based on the La₂O₃-doped WO₃nanofibers exhibit fast response and good repeatability characteristics, which are promising for acetone sensors which used by air-quality and environmental monitoring.