Abstract: Three leguminous tree species in Changchun were used as test materials to explore the differences in photosynthetic characteristics, which provided the basis for high-yield cultivation and application. The photosynthetic index was measured by portable photosynthesis instrument, and the chlorophyll content was measured by spectrophotometer. The diurnal changes of the Pn of the three leguminous tree species all showed a double-peak curve, and there was an obvious phenomenon of "noon break". The results of correlation analysis showed that PAR and Pn, Gs and Pn, PAR and Gs of Robinia pseudoacacia and Robinia pseudoacacia cv. idahoensis were significantly positively correlated （P<0.01）. There was a significant positive correlation between Tr and Ci of Robinia pseudoacacia （P<0.01）, and there was a significant positive correlation between Tr and Ci of Robinia pseudoacacia cv. Idahoensis （P<0.05）. Under the same PAR condition, Pn was as follows: Robinia pseudoacacia>Robinia pseudoacacia cv.idahoensis>Maackia amurensis, and the light utilization ability was as follows: Maackia amurensis>Robinia pseudoacacia cv.idahoensis>Robinia pseudoacacia.