Zinc　oxide　(ZnO)　is　used　as　an　electron　transport　layer　(ETL)　in　inverted　organic　solar　cells　(IOSCs)　owing　to　its　excellent　performance,　such　as　good　light　transmission　and　high　conductivity,　while　its　surface　defects　and　photocatalytic　properties　limit　the　development　of　IOSCs.　Herein,　we　apply　an　antioxidant,　syringic　acid　(SA),　to　modify　the　surface　of　ZnO　film,　which　observably　improve　the　efficiency　and　stability　of　IOSCs.　It　is　found　that　SA　can　effectively　passivate　the　surface　defects　of　ZnO　and　optimize　surface　morphology,　as　well　as　reduce　the　work　function　(WF)　of　ZnO　resulting　in　an　improvement　of　the　charge　transport　of　IOSCs.　The　power　conversion　efficiency　(PCE)　of　PM6:Y6-based　IOSCs　is　increased　from　16.19　%　to　18.18　%,　it　is　the　highest　PCE　values　of　the　single-junction　IOSCs　based　on　PM6:Y6　system　as　reported.　Meanwhile,　the　photostability　of　the　device　is　markedly　improved　due　to　SA　could　suppress　the　photocatalytic　of　ZnO　under　the　ultraviolet　aging.