Oxygen vacancies (VO) often exist in wide-bandgap metal oxide semiconductors (MOSs) as deep-level defects and undermine the reliability of various optoelectronic devices based on MOSs. Conventional methods to passivate VO defects, such as high-temperature annealing or plasma treatment, can compromise device performance. In this work, it is demonstrated that passivation of VO defects in aluminum-doped ZnO (AZO) nanoparticles can be realized through low-temperature annealing (350 oC) in an NF3 atmosphere. After the NF3 annealing the longitudinal optical phonon scattering mode in Raman spectroscopy and the visible light emission intensity in photoluminescence (PL) and the oxygen deficient-related peak in X-ray photoelectron spectroscopy (XPS) measurements decrease simultaneously, which indicates the passivation of VO defects in AZO nanoparticles. As a result, AZO nanoparticles show higher visible light reflectance and better stability of electrical conductivity owing to the suppression of deep-level light absorption and gas molecule adsorption. This work also offers insights into the passivation mechanism of VO defects in MOSs.