Abstract: Taking ambient environmental O₃(40 nmol·mol^-1) as control, the study was conducted to assess the impact of elevated O₃(80 and 160 nmol·mol^-1) on the growth, subcellular structure and reactive oxygen metabolism of turf-type Festuca arundinace in open top-chambers (OTCs). The results showed that under 14-day fumigation, the height and leaf width of F. arundinace decreased significantly, and the total biomass decreased by 43.7%, and some fully expanded leaves yellowed under 80 nmol·mol^-1 O₃. Some visible injury symptoms, brown spots and necrosis appeared in the leaves, the total biomass decreased by 46.2%, and plasma membrane became loose from the cell wall and convoluted, chloroplast and mitochondria were damaged under 160 nmol·mol^-1 O₃. The rate of superoxide anion (O₂^-·) production, hydrogen peroxide (H₂O₂) content, malonaldehyde (MDA) content and the activities of antioxidant enzymes were higher under the increasing O₃ concentrations (80 and 160 nmol·mol^-1) compared with control. Total phenolics and the antioxidant capacity increased at first and then decreased with the rise of O₃ concentration. It indicated that O₃ has already affected F. arundinace growth and antioxidative metabolism before visible injury symptom appeared. F. arundinace had an adaptive response to elevated O₃, but it could not protect itself from excessive O₃ or long-term O₃ exposure.