Abstract: Field experiments were conducted about the effect on photosynthetic characteristics, dry matter accumulation, yield and nitrogen utilization of flag leaf of Xindong18, five nitrogen application rate treatments under drip irrigation, i.e., no nitrogen (N₀), 90kg?ha_-1 of nitrogen at basal (N₁), 180kg?ha_-1 of nitrogen at basal and jointing (N₂), 270kg?ha_-1 of nitrogen at basal and jointing and booting (N₃), 360kg?ha_-1 of nitrogen at basal and jointing and twice booting (N₄). The result showed that they were increased on the content of chlorophyll and soluble protein, photosynthetic rate, LAI, total photosynthetic potential in spring at booting when increased nitrogen application rate at jointing, however, increased nitrogen application rate at booting, which were extended the duration time for the content of chlorophyll and soluble protein, photosynthetic rate and LAI, who were higher after booting on the chlorophyll and soluble protein, photosynthetic rate, LAI and total photosynthetic potential in spring of flag leaf of N₃、N₄ , and dry matter accumulation and yield of N₃、N₄were higher, increased the quantities of dry matter accumulation and yield, decreasing nitrogen use efficiency. The increased yield was mainly due to the nitrogen application and delayed the period lead to the rise for chlorophyll and soluble protein, photosynthetic rate and LAI. Therefore, in a comprehensive consideration optimal nitrogen application rates was 180-270kg.ha_-1, and his agronomic nitrogen use efficiency of nitrogen was 6.9kg?kg_-1, and obtain grain yield 8004.85kg.ha_-1.