Leaf of fruiting-node of melon is often premature senescent at the fruit ripeningstage，which is not conducive tothe transfer of nutrients and light contracted products to thefruit，and may result in a decline in yield andquality.In thisexperiment，the effects of different nitrogen and potassium application rates on the physiological characteristics of the leavesof melon in the greenhouse and the senescence of the leaf of fruiting node postponing method werestudied，so as to providea theoretical basis for rational fertilization to improve yield and quality. Five treatments were designed，which wereN2K2、N2K1、N1K2、N1K1 and NK. The results showed that the effects of different nitrogen and potassium treatments on theactivities ofSOD，POD，CAT and content of SP，MDA in melon were significantly different.With the increase of nitrogenand potassium application，the activities ofSOD，POD，CAT and content of SP increased firstly and thendecreased，thetrend of MDA content wasopposite，which decreased firstly and then increased.The rational application of nitrogen andpotassium fertilizer(NK treatment)was beneficial to slow down the decrease rate ofSOD，POD，CAT activity and SPcontent and the increase rate of MDA content，and that was more obvious at the late growth stage，while N2K2 treatmentwas not beneficial to slow down the decrease of SP，SOD，POD and CAT activity and the increase of MDAcontent，andaggravate the leaf senescence. The yield，the content of soluble solids in the center and side of melon，and the uptake ofnitrogen，phosphorus and potassium of the plant treated with NK were significantly higher than those of other treatments，however，too high or too low amount of nitrogen and potash fertilizers application seemed to be detrimental to the plant for theabsorption ofnitrogen，phosphorus andpotassium，and affected the improvement of yield and quality. Under the condition of highyieldcultivation，the optimum amount of nitrogen and potassium in soil was N 200 kg·hm -2 and K2O 300 kg·hm -2，respectively. The too high or too low amount of nitrogen and potassium will accelerate the antioxidant protective enzyme activity of leavesand increase the degradation rate of osmotic substances during the reproductive and growth stages of melons，causing theincrease of active oxygen content in plants and aggravating leafsenescence，which is unfavorable to the increase of yield and quality.