|The gas exchange and chlorophyll fluorescence parameters in leaves of eight broadleaved tree species including Magnolia liliflora Desr., M. grandiflora Linn., M. denudata Desr., Prunus mume (Sieb.) Sieb. et Zucc. cv. Meiren Men, P. mume (Sieb.) Sieb. et Zucc. f. alphandii (Carr.) Rehd, P. persica (L.) Batsch. Var. rubro-ple-na., Chimonanthus praecox (Linn.) Link and Lagerstroemia indica L. were determined under field conditions. The results showed that there were significant differences (p<0.01) in the net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (gs), water use efficiency (WUE), intrinsic water use efficiency (WUEi) among eight tree species. For the chlorophyll fluorescence parameters, the differences in the initial fluorescence (Fo), variable fluorescence (Fv), maximal fluorescence (Fm), quantum yield of PSⅡ electron transport (ΦPSⅡ) were significant at p<0.01 and the differences in potential efficiency of primary conversion of light energy of PSⅡ(Fv/Fm), the ratio of variable fluorescence to initial fluorescence (Fv/Fo), non-photochemical quenching coefficient (NPQ) were significant at p<0.05. These results indicated that the efficiency of primary conversion of light energy of PSⅡand its potential activities, the quantum yield of PSⅡ electron transport, and the potential capacity of heat dissipation differed significantly among tree species. However, there were no significant differences in maximal fluorescence in light adaptation (F′m) and actual efficiency of primary conversion of light energy of PSⅡ(F′v/F′m) among eight species. Comparatively, the mean values of Pn, Tr, WUE and WUEi were higher in three Magnoliaceae species than in three Rosaceae species, indicating that Magnoliaceae species had higher photosynthetic capacity and stronger utilization ability for water and light energy. However, the mean values of Fv/Fm, Fv/Fo, ФPSⅡ, F′v/F′m and photochemical quenching coefficient (qp) were higher in Rosaceae species than those in Magnoliaceae species, indicating that PSⅡ of the formers had higher capacity of heat dissipation and could prevent photosynthetic apparatus from damage by excessive light energy. The results also suggested that the chlorophyll fluorescence parameters differed little among species in either Magnoliaceae or Rosaceae family, indicating that species in the same family had similar leaf photosynthetic capacity. Correlation analysis among photosynthetic parameters showed that there were significantly positive correlations between Pn and Tr, Tr and gs, Fv/Fm and Fv/Fo, ФPSⅡ and F′v/F′m, qp and NPQ (p<0.01), and between Pn and gs (p<0.05). However, there were significantly negative correlations (p<0.01) between Tr, gs and WUE or WUEi, Pn and ФPSⅡ, ФPSⅡ and NPQ, qp, NPQ and F′v/F′m.