The activities of RuBPC and C4 photosynthetic enzymes in ear and flag leaf blade were examinedin wheat. The results showed that photosynthesis of ear was less sensitive to soil drought than that of flag leaf,and decrease of CO2 assimilation in flag leaf blade with water stress was more than that in ear. Compared withflag leaf, ear organs(awn, glume and lemma) had higher C4 enzyme activities and lower RuBPC activity. Un-der moderate water-stress, the increase of C4 enzyme activities was induced, and the increase was higher in earthan in flag leaf. Under severe water-stress, relatively higher C4 enzyme activities were still maintained in ear,rather than that in flag leaf. It suggests that high activities of C4 enzymes in ear may contribute to its high tol-erance of photosynthesis to water-stress.