Oxygen　vacancies　often　determine　the　electronic　structure　of　metal　oxides,　but　existing　techniques　cannot　distinguish　the　oxygen-vacancy　sites　in　the　crystal　structure.　We　report　here　that　time-resolved　optical　spectroscopy　can　solve　this　challenge　and　determine　the　spatial　locations　of　oxygen　vacancies.　Using　tungsten　oxides　as　examples,　we　identified　the　true　oxygen-vacancy　sites　in　WO2.9　and　WO2.72,　typical　derivatives　of　WO3　and　determined　their　fingerprint　optoelectronic　features.　We　find　that　a　metastable　band　with　a　three-stage　evolution　dynamics　of　the　excited　states　is　present　in　WO2.9　but　is　absent　in　WO2.72.　By　comparison　with　model　bandstructure　calculations,　this　enables　determination　of　the　most　closely　neighbored　oxygen-vacancy　pairs　in　the　crystal　structure　of　WO2.72,　for　which　two　oxygen　vacancies　are　ortho-positioned　to　a　single　W　atom　as　a　sole　configuration　among　all　O-W　bonds.　These　findings　verify　the　existence　of　preference　rules　of　oxygen　vacancies　in　metal　oxides.