Abstract: A field plot experiment was conducted to study the physiological characteristic of winter wheat with different nitrogen use efficiency Xiaoyan 22 (XY22) and Xiaoyan 6 (XY6) by measuring yield, yield components and nitrate reductase enzyme activity, leaf water potential and chlorophyll content at different key stages. The results showed that the yield, nitrate reductase enzyme activity, leaf water potential and chlorophyll content were reduced significantly under no nitrogen application. But under the condition of nitrogen application, they were significantly increased. Leaf water potential and chlorophyll content of winter wheat leaf could be kept at high level with N 150 kg/ha application. Comparing two type genotypes, the physiological activity of XY22 was more exuberant than XY6, nitrogen application strengthened this function furthermore. These results will provide the scientific basis for further selecting and breeding the genotypes with higher nitrogen use efficiency.