Abstract:Results of the study on productivity of plantation system of Castanopsis kawakamii at age 23 showed that stand biomass was 169.302 t/ha and 107.530 t/ ha for plantations with closed canopy on site class Ⅰ and Ⅱ, respectively. The biomass of tree layer for site class Ⅰ was 168.67 t/ha accounting for 99.57%, while, on class Ⅱ it was 105.47 t/ha accounting for 98.08% of the total. Index of leaf area of plantations on site class Ⅰ was 7.712 m2/m2 and 5.74lm2/m2 on site class Ⅱ. Within plantation trees with large diameter ed to have greater values in the distribution of organ biomass, especially in plantations for which early thinning were done on site class Ⅰ. It was also found that competitive index of individual trees was larger in plantations than that in natural forest stands. Theoretical value of stem biomass of intermediate trees in plantations was 124 kg that was 0.122—0.236 times of that for trees in natural stands, trees in plantations started rapidly growing 9 to 22 years earlier than those in natural stands. In plantations on site class Ⅰ the net production of individual trees was around 7000 kg/ha.a after age 13 and 5000kg/ha.a after age 16 on site class Ⅱ, but both appeared to be increased after age 23. Curves of annual and average net production did not crossed each other.