Abstract: Peach fruits of ‘Shuangjiuhong’ and ‘Kawanakajima Hakuto’ (control) were used to study the effects of MDA、relative conductivity、ABA and GA contents related to fruit firmness during 20 days before & after ripening. The results showed that MDA content、relative conductivity and ABA content of ‘Shuangjiuhong’ were significantly lower than these of ‘Kawanakajima Hakuto’ (P<0.01); however, GA content of the former was significantly higher than that of the latter since the 15th day before ripening (P<0.01). Correlation analysis showed that it was fearfully marked negative correlation among the fruit firmness, MDA content、relative conductivity and ABA content in two cultivars (P<0.01)；it was fearfully marked positive correlation between the fruit firmness and GA content in ‘Shuangjiuhong’, and marked merely positive correlation between the fruit firmness and GA content in ‘Kawanakajima Hakuto’ (P<0.05).