The fruits of peach cultivar Yuhua 3 were used as materials to investigate the changes of active oxygen and related enzymes in mitochondria respiratory metabolism during ripening of peach fruit,involving their influence on the proceeding of peach fruit senescence.The results showed that the large decrease in firmness occurred between maturity II and IV.The decrease in firmness coincided with an increase in respiratory intensity.Obvious peaks of respiratory intensity lagging to the rapid change of fruit firmness could be shown during peach ripening.Reactive oxygen species(ROS) had a cumulative process and positively correlated with respiratory intensity.During peach ripening,the content of Ca2+ increased,the activities of succinic dehydrogenase(SDH),cytochrome C oxidase(CCO),H+-ATPase,and Ca2+-ATPase decreased varying in different degree at the later step of ripening.These suggested a close relationship existed between ROS metabolism and mitochondrial respiration,namely,both ROS metabolism and mitochondrial respiration probably played important roles in ripening and senescing of peach fruit. The fruits of peach cultivar Yuhua 3 were used as materials to investigate the changes of active oxygen and related enzymes in mitochondria respiratory metabolism during ripening of peach fruit, involving their influence on the proceeding of peach fruit senescence. The results showed that the large decrease in firmness occurred between maturity II and IV. decrease in firmness coincided with an increase in respiratory intensity .Obvious peaks of respiratory intensity lagging to the rapid change of fruit firmness be be at peach ripening. reactive oxygen species (ROS) had a cumulative process and positively correlated with respiratory intensity. Fluid peach ripening, the content of Ca2 + increased, the activities of succinic dehydrogenase (SDH), cytochrome C oxidase (CCO), H + -ATPase, and Ca2 + -ATPases decreased varying in different degrees at the later step of ripening. The suggested a close relationship existed between ROS metabolism and mitochondrial respiration, namely, both ROS metabolites ism and mitochondrial respiration probably played important roles in ripening and senescing of peach fruit.