Abstract: In this study, the photosynthetic efficiency and differences of photosynthetic characteristics among different pecan varieties were evaluated. The photosynthetic characteristics and light response curves of six one-year-old pecan varieties, including ‘Mahan’, ‘Pawnee’, ‘Wichita’, ‘Stuart’, ‘Sauber’ and ‘Jinhua’, were measured with LI-6400 portable photosynthesis instrument. The results showed that the diurnal variation of net photosynthetic rate(P_n)of all these 6 pecan varieties showed asymmetric double peak curve. However, the peak value and the peak time of different varieties, were different. Monthly variation of the net photosynthetic rate of ‘Mahan’, ‘Pawnee’, ‘Wichita’ and ‘Stuart’ showed bimodal curve. However, ‘Sauber’ showed single curve. The maximum net photosynthetic rate(P_{n, max})and the light saturation point(L_SP)of ‘Mahan’ were the largest, 16.5 and 1 065 μmol/(m²·s), respectively, they were significantly higher than that of the other varieties. While the light compensation(L_CP)was significantly lower than that of the other varieties, indicating that ‘Mahan’ had better light adaptation, higher efficiency of using weak light and better shade tolerance. The differences of apparent quantum yield(A_QY)and dark respiration rate(R_d)among different pecan varieties were not significant. The photosynthetic capacity of different varieties was ‘Mahan’>‘Jinhua’> ‘Pawnee’> ‘Wichita’> ‘Sauber’> ‘Stuart’. This study showed that there were significant positive correlation between P_{n, max} and L_SP. While a significant negative correlation was found between A_QY and L_CP.