Abstract: By using aeroponics culture system, this paper studied the effects of elevated rhizosphere CO₂ concentration on the leaf photosynthesis and the fruit yield and quality of muskmelon during its anthesis-fruiting period. In the fruit development period of muskmelon, as compared with those in the control (350 μL CO₂·L^-1), the leaf chlorophyll content, net photosynthetic rate (P_n), stomatal conductance (G_s), intercellular CO₂ concentration (C_i), and the maximal photochemical efficiency of PSⅡ(F_v/F_m) in treatments 2500 and 5000 μL CO₂·L^-1 decreased to some extents, but the stomatal limitation value （L_s） increased significantly, and the variation amplitudes were larger in treatment 5000 μL CO₂·L^-1  than in treatment 2500 μL CO₂·L^-1. Under the effects of elevated rhizosphere CO₂ concentration, the fruit yield per plant and the Vc and soluble sugar contents in fruits decreased markedly, while the fruit organic acid content was in adverse. It was suggested that when the rhizosphere CO₂ concentration of muskmelon during its anthesis-fruiting period reached to 2500 μL·L^-1, the leaf photosynthesis and fruit development of muskmelon would be depressed obviously, which would result in the decrease of fruit yield and quality of muskmelon.