The influences of experimentally imposed drought stress on，photosyhthesis , photo-parameters and CO₂-parameters of potted Cupressus funebris Endl. seedlings of two different ages in the limestone area of Chongqing, were studied using a Li-6400 portable photosynthesis system. Net photosynthetic rate (Pn), transpiration (E), and stomatal conductance (Gs) of the seedlings generally decreased under drought stress, but 1-year old seedlings decreased more than 5-year old seedlings. Intercellular concentration (Ci) of 1-year seedlings increased with aggravating drought stress while the stomatal limitation value (Ls ) decreased. In contrast, Ci of 5-year seedlings decreased and Ls increased before they suffered serious drought stress, but they had the same trend as 1-year seedlings under serious stress. These results implied that the photosynthetic depression of 1-year seedlings was caused by non-stomatal limitation, while the depression of Pn in 5-year seedlings was predominantly due to stomatal limitation before suffering serious stress, but transferred to non-stomatal limitation after suffering serious stress. Water use efficiency (WUE) in 1-year seedlings decreased with the aggravation of drought stress, but 5-year seedlings showed the reversed trend, indicating that 5-year seedlings had greater drought resistance. Under drought stress apparent quantum yield (AQY), carboxylation efficiency (CE) and photosynthetic ability (A0) of 1-year seedlings decreased, while light compensation point（LCP）, CO₂ compensation point（Γ）, light respiration rate（RP） and dark respiration rate（Rd）increased. For 5-year seedlings, AQY, LCP, RP and A0showed similar trends, but CE and Γ decreased at first, then increased at the end, while Rd followed the reversed pattern. This also indicates that 5-year seedlings could cope better with drought stress.