Abstract: The relationship between nitrate nutrition and active oxygen metabolism in the pre-senescent wheat variety L14 under heat-stress condition was investigated.The results indicated: under the conditions of either moderate or severe heat stress, nitrogen nutrition improved the activity of enzymes(SOD, CAT) related to active oxygen metabolism, reduced the harm of ex-oxidation (MDA) of membrane lipid.However, the change of non-enzymic components (AsA, GSH) in active oxygen metabolism showed difference.The contents of AsA apparently rise but that of GSH appear insensitive with increment of nitrogen concentration during moderate heat-stress; nitrogen nutrition evidently promoted reduction of contents of AsA and GSH at 42℃heat stress.It means nitrogen nutrition can raise scavenging capacity of active oxygen, reduce its harming function and finally alleviate the high temperature stress when the stress temperature is lower than about 37℃.