Abstract: To assess the effect of pollution by compound heavy metals in antimony mine area soil on physiological characteristics of photosynthesis of Magnolia denudate, the pot experiments were conducted for Magnolia denudata seedlings cultivated in heavily polluted soil, slightly polluted soil, and not polluted soil. And the diurnal variation of physiological characteristics of photosynthesis of Magnolia denudate under heavy metals stress were studied with the Li-6400 portable photosynthetic system. The following results were found in the experiments: in pot experiments the diurnal variation of net photosynthetic rate (Pn)of Lianmeng and Duizhao presented a single-peak curve, and the maximum value occurred at about 12:30, the diurnal variation of net photosynthetic rate (Pn) of Changlongjie was unregular, the photosynthetic capacity of three treatments from high to low was Lianmeng ＞ Duizhao＞ Changlongjie, heavy metals stress had an inhibitory effect on photosynthesis of plant; There was a significant positive correlation between stomatal conductance(Cs) and transpiration rate (Tr) during the diurnal variation(Lianmeng 0.981**, Changlongjie 0.829*, Duizhao 0.87*). The transpiration rate (Tr) was determined by the status of stomatal activity to a great extent. So the controlling factor of photosynthetic rate was non-stomatal limitation. It was also found that the heavier the metal pollution the weaker is the ability of Magnolia denudate to adapt to environmental conditions (Duizhao ＞Lianmeng＞ Changlongjie).