Abstract: The observation of the daily photosynthesis variation of different green organs of winter wheat in the grain-fiUing stage show that there is an obvious difference between the largest photosynthetic efficiencies of different green organs in one day． It behaves as flag leaf>stem> awn>sheath>spike without awn．The green organs except the leaf also have strong photosynthetic capability．During the daytime，the photosynthesis rate of flag leaf drops very fast in the afternoon，but the green organs keep higher photosynthetic efficiency．The photo-compensation points of leaf，stem and sheath are very near，but the spike’s is much higher．There is no obvious noon break of spike．