Abstract: The main photosynthetic characteristics of the main urban forest species Pinus tabulaefomis and Ginkgo biloba in Shenyang City were analyzed in open-top chambers under elevated CO2 concentration. Net photosynthetic rates and soluble sugar, starch and soluble protein content of the leaves of the two species under elevated CO2 concentration (700 mmol.mol-1) were close to or higher than that of respective controls (natural CO2 concentration), whose contents were increased differently between species. The responses of chlorophyll content and ratio of Chl a/Chl b under elevated CO2 concentration were not identical for the two species. As well, chlorophyll content increased and ratio of Chl a/Chl b decreased in P. tabulaefomis leaves under elevated CO2 concentration, whereas chlorophyll content of G. biloba leaves increased during the earlier growing season, decreased in the later growing season, and the ratio of Chl a/Chl b responded contrarily, which indicated complexity in the response to elevated CO2 concentration of tree species in an urban forest. Both tree species showed no photosynthetic acclimation to elevated CO2 concentration.