Abstract:The article deals with the effect of CO2 enrichment on the Quercus liaotungensis, a dominant of typical and natural deciduous broad-leaved mixed forests in the warm temperate China. The results show that the stomatal resistance, the transpiration rate, the dark respiration rate, the net photosynthesis rate, the diurnal net photosynthates and the water use efficiency of the plants grown under the CO2-enriched environment were 106 %, 92%, 98.9%, 155%, 172% and 179 % of those grown under the CO2-unenriched environment (CK),respectively. The response of the plants to the CO2 enrichment were more obvious in the growing peak period(June, July), in terms of the last three characters mentioned above. The leaf area, the leaf dry weight and the plant height of the plants growing under the CO2-enriched environment were 107%, 140% and 331% of those growing under CK, respectively. It is evident that the plants responded positively to the CO2-enrichment in terms of most of the physiological and growth characters investigated, suggesting that, as long as other environment are proper for the plant, the doubled CO2 concentration may fertilize the plant and increase their physiological process and bioproductivity.