After exposure of one-year old seedlings ofSwietenia macrophylla to an overnight temperature (13°C, 19°C, 25°C, 31°C or 35°C), the leaf net photosynthetic rate (P n) was researched through measuring photosynthetic light-response curves at 360 μmol·mol−1 CO2, and photosynthetic CO2-response curves at light-saturated intensity (1500 μmol·m−2·s−1). The optimal temperature for photosynthesis measured at 360 μmol·mol−1 CO2 was from 25°C to 31°C, but which was from 31°C to 35°C at saturating CO2 concentration. At temperature of below 25°C, the decline inP n was mainly due to the drop in carboxylation efficiency (C e), while as temperature was over 31°C, the reduction inP n resulted from both decrease inC e and increase in leaf respiration. The CO2-induced stimulation of photosynthesis was strongly inhibited at temperatures below 13°C. The results showed that, the leaf photosynthesis of tropical evergreen plants should not be accelerated at low temperature in winter season with elevated CO2 concentration in the future.