Abstract: The photosynthesis of 6 superior eucalyptus clones were tested.The results were as follows: The net photosynthetic rate Pn of E.urophylla and irradiance had a conic correlation evidently, the light response saturation point was 1 967.7 μmol·m-2 ·s-1. All photosynthesis were significantly different among clones, Pn and transpiration rate E of the eucalyptus clones were higher than other local broad-leaved tree species.Some clones of E.urophylla × E.grandis and E.urophylla × E.tereticornis grew not only faster than those of clones of E.urophylla × E.camaldulensis and E.urophylla, but also with high water used efficiency WUE and stronger ability of photosynthesis.The daily variation of Pn、E and leaf conductance gs were similar,but leaves of intercellular CO2 concentration Ci and Pn showed the other way round in the diurnal courses. Pn, gs and WUE had positive correlation with the H, DBH and SV, these results could be useful for early selection of superior eucalyptus clones.