Abstract: In order to research the activities of defense enzymes in muskmelon, the oxalate, salicylic acid and BTH were used to treat 2-leaf muskmelon leaves in different concentrations. The results showed that after treated by oxalate, the activities of β-1,3-glucosidase and peroxidase (POD) in 2-leaf muskmelon leaves were higher than that in the control. And the β-1,3-glucosidase activity increased 2.7 to 3.9 times, POD activity increased 3.5 to 4.8 times 9 days after the treatment. But PAL activity could not be induced by oxalate. After treated by SA and BTH, the activities of β-1,3-glucosidase, POD and PAL were higher than that of the control obviously. And the β-1,3-glucosidase activity increased 1.9 to 3.8 times, POD activity increased 3 to 5.5 times and PAL activity increased 1.8 to 5.2 times 7 days after the treatment.