Abstract: The photosynthetic and transpiration characteristics of Salvia miltiorrhiza in Prunus dulcis and S.miltiorrhiza tree-herb system were studied using the Li-COR 6400 portable photosynthetic system.The study provides theoretical basis for developing tree-herb complex system.The results are as follows:1) the diurnal variation of light intensity at the middle experimental site between the popular rows demonstrates a curve with one peak, the same as the control,but the value of light intensity on the peak is lower than that of the control.The diurnal change of light at the east and west sites are symmetrical.The peak of the former appeared in the morning,and that of the latter in the afternoon.The average diurnal light intensities at the middle site,east rows and west rows are 25.6%,68.5% and 62.6% lower than the control;the average diurnal light intensities among different sites is significant at P=0.05 level.2) AQ curve and Pn/C_i curve were analyzed with SPSS statistical program.The results show that the critical points of light saturation and light compensation,and apparent quantum yield are 236.4 μmol/(m²·s),15.88 μmol/(m²·s) and 0.056 1 mol/mol.CO₂ saturation point,compensation point and carboxylation efficiency are 30 μmol/mol,800 μmol/mol and 0.075 2.S.miltiorrhiza is a C₃ plant.3) The photosynthetic rate and transpiration rate of S.miltiorrhiza in the tree-herb system decline,and the difference of those values of different sites is significant at P=0.05 level,the regularity of their diurnal variation curves also changes.