Abstract:The results of the determination are as follows: 1. The photosynthetic rate of E. citriodora is 58.8% (half leaf method) and 25.3% (warburg microrespirometer method) higher than that of B. hsienmu. The respiratory intensity of B. hsienrnu is 3.2 times (half leaf method) and 1.3 time (warburg microrespirometer method) as high as that of E. citriodora. The rate of photorespiration of B. hsienrnu is 70.3 times as high as that of E. citriodira. 2. The efficiency of the dry matter accumulation of E. citriodora is higher than that of B. hsienmu. 3. The cell biological characteristics (structure of leaves, amount of stomata, thickness of leaves, layers and thickness of palisade cell, density of palisade cell etc. ) of E. citriodora are more advantageous to the photosynthesis than that of B. hsienmu. 4. There are positive correlations between chlorophyll contents and net photosynthesis rate in two tree species. 5. There are positive correlations between N contents, soluble protein of leaves and net photosynthesis rate in two tree species. 6. Efficiency of N utilization for E. citriodora is 15.4% higher than that of B. hsienmu.