Abstract: 【Objective】Analyze the physiology of Paulownia fortunei etiolation, in order to establish a theoretical basis for researching new Paulownia varieties. 【Method】The photosynthetic pigment content, photosynthetic diurnal changes, antioxidant enzyme activity and MDA content of P.fortunei, P. jianshiensis, P. catalpifolia,and a recently discovered P. fortunei etiolation mutant were analyzed.【Result】The chlorophyll a,chlorophyll b,total chlorophyll and carotenoid levels of the mutant were reduced, with that of chlorophyll b reduced remarkably.Diurnal variation in the photosynthetic rate and transpiration rate of the etiolation mutant was generally lower than that of the other species. However, there was no significant difference among the stomatal conductance of the mutant and species, and its value generally decreased.Meanwhile, antioxidant enzyme activity, MDA content and diurnal variation in intercellular CO₂concentration were higher in the etiolation mutant than in the other species.【Conclusion】Reduced photosynthetic pigment contents were the main cause of leaf yellowing, which impedes light harvesting and photosynthesis, enhances the activity of antioxidant enzymes, increases plant resistance, reduces the damage of active oxygen, and maintains normal plant growth.