【Objective】The objective of the present study was to investigate the effect of  1-methylcyclopropene （1-MCP） treatment on post-harvest physio-biochemical changes and storage quality of papaya. 【Method】Post-harvest changes in physio-biochemical parameters （membrane permeability， respiration rate， titrable acidity and chlorophyll， protein and vitamin C content）， activities of antioxidative enzymes （superoxide dismutase: SOD； peroxidase: POD） and free oxygen radicals （superoxide anion: ■） were investigated during 13 d storage of Risheng papaya treated two times with 1-MCP （1 mg/L） at room temperature. 【Result】The treatment of 1-MCP was found to delay the peak time of respiration rate， inhibit decomposition of chlorophyll， decrease the superoxide anion （■） content and membrane permeability， and increase protein content and antioxidative enzyme activities. However， it also inhibited the increase in titrable acidity and VC content. The effects of second time application of 1-MCP treatment were more pronounced. 【Conclusion】Two times application of 1-MCP （1 mg/L） was found to enhance the post-harvest quality of papaya fruits during its long term storage.