To explore the effect of chilling stress on antioxidant activities in the leaves of chilling tolerance ruble tree ‘Zhanshi 327-13’ and chilling sensitive variety ‘Wenchang 217’,we treated the seedlings of both varieties by chilling stress at 8 ℃/8 (day/night).Antioxidant activities and the related physiological parameters were determined every day from the beginning of treatment.Then,the content of H₂O₂ in guard cells was measured by laser confocal microscope in different time after chilling stress.The results showed that:(1)The released rate of superoxide radical anion and the activities of superoxide dismutase (SOD),catalase (CAT),peroxidase (POD) and APX in the leaves of ‘Zhanshi 327-13’ and ‘Wenchang 217’ increased first and then decreased under chilling stress;And the activities of anti-oxidases in the leaves of ‘Zhanshi 327-13’ were constantly higher than those in ‘Wenchang 217’ during the whole experiment;The content of H₂O₂ maximized at the first day in the leaves of ‘Zhanshi 327-13’ but maximized at the third day for ‘Wenchang 217’ after chilling stress.(2)The content of H₂O₂ in the leaves was consistent with that in the guard cells.Our experimental results suggested that the quick accumulation of O^-·₂ and H₂O₂ in ‘Zhanshi 327-13’ probably played a role in molecular signaling pathways through which increased the antioxidant activities,decreased oxidant stress and kept lower content of TBARS.Lower relative conductivity was maintained after chilling stress in the leaves of ‘Zhanshi 327-13’ so as to increase the tolerance to chilling.