Abstract: Moringa (Moringa oleifera Lam.) is a kind of tropical plants with high economic value. It has been successfully introduced in Shaoguan. The variation of photosynthetic rates of Moringa under different CO2 concentrations was studied. The results showed that net photosynthesis rate of Moringa under different CO2 concentrations (3 250~400 L/L) was different. The highest net photosynthetic rate was obtained under the CO2 concentration between 700~450 L/L. After that, continuing increase of CO2 concentration will lead to the decrease of net photosynthesis rate of Moringa. The higher the CO2 concentration increase, the greater the decline of net photosynthesis will be, even drop to negative. With the increase of CO2 concentration in leaf chamber, intercellular CO2 concentration will be increased. Meanwhile, the variation of stomatal conductance and transpiration rate were not significant.