Abstract: A field experiment was conducted in Urumqi and Changji to investigate the effect of nitrogen application timing on protein constitute and its dynamic change in wheat grain during 2002-2003. Split plot design was adapted in this (experiment.) Two cultivars, GC8901 and XD23, as main plots and N application timing, top-dressing at re-greening (RG), jointing(JT) and booting(BT) stage, respectively, as subplots. The results showed that under the condition of same N application rate, wheat yield in the treatment of RG was significant higher than that of JT and BT, which indicated that top-dressing N at jointing stage was of great advantage to get a higher grain yield. The albumin and globulin content of grain decreased and gliadin and glutenin increased due to the lag of N application timing. It was observed that the application of nitrogen fertilizer at booting stage could increase glutenin content markedly, which was favorable for the improvement of wheat processing quality. Whereas, we could conclude that the responses of wheat quality to nitrogen application timing was not in agreement with that of grain yield of wheat. The ratio of glutenin to gliadin was enhanced due to the lagging of N application, but the response of different cultivars on the lagging of N application varied with the change of plantingloci.