Tungsten oxide nanowire has a great potential application to gas sensor with high sensitivity and low power consumption. Its gas-sensing properties can be greatly improved after doping the nanowires. In this paper, vanadium (V)-doped W18O49 nanowires are synthesized by solvothermal method, with WCl6 serving as precursor and NH4VO3 as dopant. The microstructures of the pure and the doped nanowires are characterized by using SEM, TEM, XRD, and XPS techniques, and the NO2-sensing properties are evaluated in a static gas-sensing measurement system. The obtained results indicate that the introduction of V dopant suppresses the growth of one-dimensional nanowires along their axis direction and causes the secondary assembly of nanowires bundles. At room temperature, the V-doped W18O49 nanowires show an abnormal p-type response characteristic upon being exposed to NO2 gas, and a conductivity transition from p-to n-type occurs when operating temperature is raised to about 110 ℃. The doped nanowires-based sensor exhibits obvious sensitivity and good response stability to dilute NO2 gas of 80 ppb at room temperature. The origin for the p-n conductivity transition and the high sensitivity at room temperature for the V-doped W18O49 nanowires are analyzed, and they can be attributed to the strong surface adsorption of oxygen and NO2 molecules due to the large density of unstable surface states.