Abstract:This paper mainly deals with the changes of the rate of net photosynthesis(Pn)which varied with leaf age,including primordial leaf of seedlingsand 1 or 2-year-old needles of young trees of Pinus massoniana.Thehabitat,productive structure and the variation of net photosynthesis and netprimary productivity were also studied of the groves which were.formed bynatural regeneration.The research results showed that peak value of Pn occurred during July for primordial leaves and the rate of Pn varied in abiparabolic curve for 1 or 2-year-old needles.In order to improve the net primary productivity of the natural stands of this species,the productive structureof the groves should be properly controlled.