An experiment was conducted to study the characters of epidermis stomata and leaf tissue structure of Ligustrum obtusifolium seedlings exposed to elevated O_3 concentration (160nmol ? mol~(-1)) for 136 days in open top chamber (OTC). The results showed that elevated O_3 decreased the stomatal length,width,perimeter and area in adaxial leaves of L. obtusifolium by12.9%, 8.4%, 8.2%, and 15.0%, respectively, while decreased by 16.8%, 9.8%, 13. 3%,and 23.6%,respectively in abaxial leaves. The stomatal aperture decreased by 69.2% in adaxialleaves (P <0.05),and decreased by 39.3% in abaxial leaves (P <0.05). The elevated O_3 concentration did not have significant effect on stomatal density (P >0.05). Under elevated O_3,thethickness of palisade tissue and thickness ratio of palisade tissue to spongy tissue in adaxial leavesincreased by 10. 2% and 28. 9%,respectively, and increased by 7. 3% and 29. 5% in abaxialleaves, respectively (P <0. 01). The thickness of spongy tissue decreased by 15. 1% in adaxialleaves, and decreased by 16. 8% in abaxial leaves (P<0. 01). The thickness of upper and lowerepidermis increased by 18. 9% and 23. 1% in adaxial leaves, respectively, and increased by11.5% and 16.0% in abaxial leaves (P<0.05). The leaf thickness increased slightly (P>0. 05).These results provided new evidence for the research in the effects of elevated O_3 on leaf tissuestructure and function of urban plants under the background of global climate change.