An experiment was conducted to study the variations of the physiological indexes in leaves of Trifolium repens, Poa pratensis and Festuca arundinacea exposed to elevated O₃ concentrations (80 and 120 nmol·mol^-1) in open top chambers (OTCS). The results showed that three turfgrass species showed different injury symptoms induced by O₃ stress, while brown injury spots appeared on T. repens first. Elevated O₃ significantly inhibited the growth of the three grass species and significantly increased the content of malondialdehyde (MDA) and the activities of superoxide dismutase (SOD) and peroxidase (POD) (P<0.05). Elevated O₃ significantly increased the content of abscisic acid (ABA) in leaves of P. pratensis and F. arundinacea, while T. repens showed a decreasing trend after an initial increase. The results showed that T. repens is most sensitive to high concentrations of O₃ while F. arundinacea least.