By the methods of chamberbased and eddy covariance measurements, the
CO2 exchange of dominant tree species Pometia tomentosa and Gironniera subaequalis at leaf and canopy levels in the tropical seasonal rain forest of Xishuangbanna was measured in different seasons of 2004. The results showed that for the two tree species, the maximum net photosynthesis (Pmax A) of canopy based on chamberbased measurement ranked in the order of rainy season (RS)> end of rainy season (ERS)>foggycool season (FS)>dryhot season (DS), and the dark respiration rate (Rd) of leaf was RS>ERS>DS>FS. The PmaxB based on eddy covariance measurement was in the same order as that based on chamberbased measurement, while the canopy respirati
on rate (Re) was RS>DS>FS>ERS. The maximum net photosynthetic rate of canopy in different seasons measured by the two methods had a comparatively small difference, ranging from 0.9 to 2.0 μmol·m-2·s-1.