To study the effects of elevated CO₂ concentration (CO₂) on the leaf photosynthesis and chlorophyll fluorescence parameters in Dracaena angustifolia and Philodenron selloum,we exposed the seedlings of D.angustifolia and P.selloum to either ambient CO₂［CK,(390±30) μmol·mol^-1］ or elevated CO₂［T₁,(780±30) μmol·mol^-1;T₂,(1 560±30) μmol·mol^-1］ in an open top chamber.The results showed that:(1)Leaf area and plant height of seedlings significantly raised with the increase of CO₂ concentration.(2)Under the high CO₂ concentration,the net photosynthetic rate (P_n) was higher earlier and lower later,but their stomatal conductance (G_s) and transpiration rate (T_r) significantly reduced.(3)The ratio of variable fluorescence to maximal fluorescence (F_v/F_m) and the actual photochemical efficiency (Φ_PSⅡ) tend to increased and then decreased with the CO₂ concentration raised.Photochemical quenching coefficient (q_P) also had the same trend,but the difference was not significant.On the contrary,non photochemical quenching coefficient (NPQ) tends to decrease earlier and increased later.The increasing CO₂ concentration in a certain extent might be beneficial for increasing net photosynthetic rate and the vegetative growth,but the promotion decreased slowly and then disappear if CO₂ enrichment prolonged.The performance of P.selloum seedling was more outstanding.It suggested that the higher CO₂ concentration could injure the structure of leaf photosystem Ⅱ and consequently decreased the leaf photosynthetic capacity in the late growth phase of D.angustifolia and P.selloum.