Ambient ozone (O₃) has become an important ecological factor affecting plant growth and development. In order to investigate the effects of surface O₃ pollution on the morphological characteristics and nutritional indexes of vegetables, Lactuca sativa var. roman was employed for fumigation experiment in open-top chamber (OTC). Four O₃ fumigation concentrations (NF: unfiltered ambient air; NF40: ambient air +40 nmol/mol; NF80: ambient air +80 nmol/mol; NF120: ambient air +120 nmol/mol) were set up in the experiment. Three repeating groups were set for each treatment to analyze and evaluate the visible injuries, production, leaf anatomical characteristics of the plants, and nutritional indicators of edible parts caused by O₃ pollution. The results showed that: (1) O₃ fumigation caused irreversible visible injury to lettuce leaves, which showed light yellow spots and brown spots. With the prolongation of fumigation time, the leaves showed yellow, large necrotic patches, and accelerated senescence. (2) The high concentration of ambient O₃ significantly reduced plant height at the growth stage (P<0.05). Compared with the NF group, the NF40, NF80, and NF120 groups decreased the biomass by 5.90%, 14.99%, and 39.21%, respectively. (3) Stomatal density increased and stomatal aperture decreased with higher O₃ fumigation concentration. Thickness of leaf and its spongy tissue and palisade tissue were significantly negatively correlated with AOT40 (P<0.05). (4) The high concentration of O₃ exposure caused a significant decrease in the content of Ca, Na, Fe, Zn, and Mg in the vegetables, and an increase in the content of fat and protein, which altered the nutritional indicators of the Lactuca sativa var. roman. The study showed that Lactuca sativa var. roman was sensitive to environmental O₃ pollution. Its growth, development and nutritional indexes changed significantly under O₃ stress conditions. Currently, there are fewer studies on the effects of O₃ pollution on the morphological characteristics of vegetables, this study systematically explore the changes of morphological indicators such as blade thickness, palisade tissue, spongy tissue, stomatal density and aperture of vegetables under ozone pollution conditions. The quality of vegetables is an important aspect related to the "Three Rural Issues", this study explores the effects of ozone pollution on the yield and nutritional indicators of vegetables, which can provide scientific reference for the production of vegetables under the O₃ pollution conditions.