Abstract: The biomass and net primary production of 28—37 year-old natural Pinus henryi forests were investigated and analyzed. The results showed that, the biomass of arbor layer, undergrowth (including herb) layer together with the dead materials were 81.28 t/ha, 1.45 t/ ha and 11.16t/ha respectively. The net primary production of arbor layer was 6.94t/ha·a, of which leaf accounted for about 45%, extinction coefficient of the forest had a average of 0.33. The biomass and net primary production of the stands were closely proportional to LAI. Regarding the aboveground production structure, the branch weight was mainly distributed in the mid-lower part of the crown, and leaf weight percentage increased in the lower part of the crown with needle age. The length of root system for P. henryi forests was about 99.4km/ha, of which fine roots accounted for 58% of the total.