Abstract: The effects of nitrogen supply on photosynthetic characteristics at late developing stage in superhigh-yield winter wheat were studied under field conditions. The net photosynthesis rate（Pn）, intercellular CO2 concentration（Ci） and stomatal conductance（Gs） in superhigh-yield winter wheat were measured using Li-6400 Portable Photosynthesis System with an open flow gas exchange system. The results showed that nitrogen supply improved the photosynthetic characteristics at late developing stages of superhigh-yield winter wheat. The net photosynthesis rate was enhanced with the increasing of nitrogen supply. However, surplus nitrogen supply (N 375 kg/hm2) accelerated the leaf senescence. The highest grain yield was observed in the treatment with N 300 kg/hm2 applied.