Abstract: Effects of different densities and nitrogen levels on activities of nitrogen metabolism enzymes in flag leaf and grain quality were studied using triticale variety cv. Dongnong 5305. The results showed that the activities of nitrate reducase(NR) and glutamine synthetase(GS) of flag leaves increased, while endopeptidase and aminopeptidase of flag leaves decreased, and the soluble protein contents of flag leaves increased with the decreasing of density and increase of nitrogen fertilizer. Grain yield under density of 3 million/ha and N 75 kg/ha was higher than other treatments. Under density of 3 million/ha and N 150 kg/ha, contents of protein, amino acid and lysine of grain were the most. There was significant positive correlation between grain protein content and GS activities of flag leaves, while there was negative correlation with grain protein content and proteolytic activities. By reducing the density and increasing nitrogen fertilizer, the nitrogen assimilation of leaf after flowering was improved, the ability of leaf protein degradation was depressed, and leaf senescence was delayed. To the effect, we concluded that soluble protein content of flag leaves could be used as a physiological index for protein metabolism.