ZnO　nanocrystals　with　different　oxygen　defects　(type　and　concentration)　are　successfully　prepared　via　the　templating　method　in　Nafion　membranes.　Photoluminescence　and　infrared　characterizations　reveal　that　the　concentration　of　oxygen　defects　(oxygen　vacancy　and　interstitial　oxygen)　is　quite　different　for　the　samples　prepared　via　different　synthesis　processes.　Photocatalytic　activity　measurements　show　that　the　sample　with　a　higher　amount　of　oxygen　defects　exhibits　excellent　activity　toward　the　degradation　of　rhodamine　B.　Compared　with　bulk　ZnO,　ZnO　nanocrystals　embedded　in　Nafion　membranes　have　an　antiphotocorrosion　property.　The　possible　photocatalytic　mechanism　is　discussed　in　detail,　and　the　oxygen　defects　are　proposed　to　be　the　active　sites　of　the　ZnO　photocatalyst.　©　2009　American　Chemical　Society.