The photosynthetic oxygen evolution rate,Hill reaction activity of seedlings and photosynthetic parameter,Pn-Ci curve and some source-sink metabolism related enzyme activities and substance content of flag leaves were measured by using two wheat near isogenic lines(NILs)with significant differences in the photosynthetic rate of the 154(high photosynthetic rate)and 212(low photosynthetic rate)lines as materials.The results showed that the maximal carboxylation efficiency(Vcmax)and Hill reaction activity were higher in line 154 than that of line 212.The Pn in flag leaves of line 154 was significantly higher than that of line 212 during the anthesis to grain filling stage.