Abstract: In this paper, the biomass and net primary productivity of two dominance species, Cryptocarya concinna and C. chinensis, of forest vegetation on Dinghushan Mountain are studied. After surveying quadrat samples, the total numbers of the two species and the height and base area of every tree are measured. According to the data on harvested trees, the growth relation formulas of the varied parts of a plant are built, and then the biomass of the two populations are calculated. The photosynthetic rates and respiration rates of the two populations are also measured, and their photosynthetic values and respiration values as well as their net primary productivity are calculated.The results show that the biomass of Cryptocarya concinna is 68.208 t· ha-1 (fresh weight) or 39.053 t· ha-1 (dry weight); the biomass of C. chinensis, 43.733 t· ha-1 (fresh weight) or 24,092 t· ha-1 (dry weight). The net primary productivities of Cryptocarya concinna and C. chinensis are 2.384 t·ha-1·a-1 and 1.193 t·ha-1·a-1. According to the biomass and net primary productivitys of the two populations, the populations of Cryptocarya concinna and C. chinensis hold an importnat position and play an important role in the community.