Abstract: Apple fruit were dipped in 100mg·L- 1acibenzolar- S- methyl ( ASM) for 10 min, then inoculated with P.expansum and stored at room temperature to determine lesion diameter and ascorbate- glutathione ( As A- GSH) cycle. The results indicated that ASM treatment significantly decreased lesion diameter of fruit, enhanced the content of hydrogen peroxide ( H2O2) , inhibited the activity of catalase ( CAT) , increased ascorbate peroxidase ( APX) , glutathione reductase ( GR) , monodehydroascorbate reductase ( MDAR) , dehydroascorbate reductase ( DHAR) activities, and also enhanced the content of ascorbic acid ( As A) and reduced glutathione ( GSH) .These results suggested that ASM induced disease resistance by inhibiting CAT activity to accumulate high level of H2O2 and activating other defense responses in apple fruit, enhancing anti- oxidative enzymes activity and antioxidants contents in As A- GSH cycle were beneficial to eliminate damage of over accumulation of H2O2 to fruit.