Abstract: Muskmelon fruit( cv.Jinhongbao) was used as material to study the effect of three low storage temperatures( 3,7,9℃) on the production rate of superoxide anion( O-2·),accumulation of hydrogen peroxide( H2O2) and the activities of superoxide dismutase( SOD),catalase( CAT),glutathione reductase( GR) and ascorbate peroxidase( APX) during storage.The results showed that the production rate of O-2·was increased at the early stage( 4d) of storage at 7℃ and 9℃,but significantly enhanced at the late stage( 12d) of storage at 3℃.The accumulation of H2O2 was significantly increased at the early stage of storage at 3℃.However,it was gradually increased in the mid( 8d) and late( 12d) stage of storage at 7℃ and 9℃.At the early stage of storage,the activities of SOD,GR and APX in muskmelons stored at 7℃ were higher than that stored at 3℃ and 9℃,and the activity of CAT in fruit was the lowest at 3℃.These results indicated that a large accumulation of H2O2 and the lower activities of the antioxidant enzymes in fruit stored at 3℃ may lead to chilling injury of muskmelons. The fruit stored at 7℃keep the balance of reactive oxygen species production and scavenging,indicating 7℃ is suitable temperature for storage of muskmelons.