Surface　oxygen　vacancy　has　been　investigated　extensively　due　to　its　great　influence　on　photocatalysis　in　recent　years.　Among　these　investigations,　the　location　of　surface　defects　is　found　to　be　a　key　factor　during　the　photocatalytic　procedure.　Especially　when　a　crystal　facet　is　involved,　the　synergistic　action　between　these　two　factors　may　greatly　increase　the　photocatalytic　efficiency.　Location　of　defects　would　greatly　help　in　understanding　the　mechanism　of　this　coupling　action.　Without　an　available　technique,　however,　it　is　very　difficult　to　gain　the　position　information　directly.　In　this　paper,　we　provide　a　low-cost　and　visualized　method　to　solve　this　problem　via　in　situ　reduction　of　Au.　TiO2　with　surface　oxygen　vacancy　on　a　specific　area　is　synthesized　via　a　photochemical　reaction.　Then　the　Au　ion　was　reduced　at　the　place　where　oxygen　vacancy　exists　on　the　TiO2　surface.　Hence,　the　localization　of　surface　vacancy　will　be　determined　by　examining　the　location　of　Au　particles.　Moreover,　application　of　this　method　can　be　extended　to　other　surface　defects　such　as　oxygen　vacancy　on　oxide　semiconductors,　Ti3+　in　TiO2,　Zn　vacancy　on　ZnO,　etc.　This　technique　is　helpful　for　understanding　how　surface　defects　affect　the　properties　of　semiconductors.