This study was conducted with ginseng plants to investigate photosynthetic response to changes of light intensity and leaf temperature. $CO_2$ uptake in diurnal course was highest in the first phase (8 00~5 : 30 Am.) on May 30, 1992. In $CO_2$ uptake related to stomatal conductance, these relationship was synchronized in diurnal course, but relationship between TEX>$CO_2$</TEX> uptake and intercellular $CO_2$ concentration in diurnal course was synchronized oppositely. Leaf temperature and light intensity at the highest $CO_2$ uptake were in the range of 23~$24^{circ}C$) and 95$mu$mol.$m^{-2}$.$s^{-1}$), $CO_2$ , respectively. In response to an increasing light intensity under a constant leaf temperature ($18^{circ}C$), $CO_2$ uptake was increased throughout the light intensity sequence up to 250$mu$mol.$m^{-2}$.$s^{-1}$), $CO_2$ When $CO_2$ uptake was measured with a series of leaf temperature under a constant light intensity (250 $mu$mol.$m^{-2}$.$s^{-1}$), $CO_2$ uptake was highest at $18^{circ}C$ as a 4.1$mu$mol.$m^{-2}$.$s^{-1}$), $CO_2$ . Similar changes were also observed in stomatal conductance and intercellular $CO_2$ concentration. Evidences from several approaches indicate that synchronization of $CO_2$ uptake, stomatal conductance and intercellular $CO_2$ concentration were closely inter-related and changes of leaf temperature iuluenced the photo-response in photosynthetic processes.