Photosynthesis is the basis of energy flow in natural ecosystems and plants’ photosynthesis characteristics determine primary productivity of an ecosystem. Plant photosynthetic characteristics, though varying with different plant developmental stages, are not only an important factor influencing energy input of the eco-system, but also a major driving factor of regeneration and development of plant communities. In a forest ecosystem, photosynthetic physiologico-ecological characteristics of its dominant species affects the structure and function of the whole eco-system. The Funiu Mountain National Nature Reserve, sitting in the transitional zone between the north subtropics and the south warm-temperate, has preserved an intact type of forest ecosystem. Quercusvariabilis, as its main dominant species in areas of low altitude, regenerates nicely forming distinct layers. Photosynthesis of the plants of different development stages (arbor, shrub and seedling) was measured with a Li-6400 photosynthetic meter and a fluorimeter in the field, and chlorophyll contents in the plants determined in the laboratory. Results show that（1）the plant at its seedling stage is the highest in apparent quantum yield and in chlorophyll content, but the lowest in dark respiration rate and in light compensation point; （2）the plant at its arbor stage is the highest in high-light adaptability, but the lowest in chlorophyll content, and does not show any phenomenon of midday depression, and diurnal variation of its net photosynthesis at different layers is mainly governed by light intensity;（3）the plant at its arbor stage is the highest in PSⅡmaximum photochemical quantum yield, while the plant at its seeding, the lowest; and（4）the plant, regardless of growth stage, is higher in the morning than in the afternoon in stomatal conductance and in transpiration rate; and in water use efficiency, too, at all the stages, except the arbor stage, when it goes reversely. Such divergences of the plant in photosynthetic characteristics with the developmental stage enable it to adapt to different environments. That’s why the plants grow nicely at all stages, showing strong regeneration ability and an inherent impetus towards positive succession.