Abstract: In the Broadleaved-korean pine forest, the dry weight loss of the leaf of Pinus koreansis, Quercus mongloica, Acer mono., Betula platyphyla, Ulumus propinqua, Tilia amurrensis, and Populus davadiana after 300 days situ decomposition, is 24.2%, 37.6%, 30.8%, 44%, 47%, 50.6% and 55.6% respectively. During the incubation,the dry weight loss has a lineary relationship (R=0.99) with the tested chemical properties of the leavies. In the firest several months, the contents of the lignin and total nitrogen in the leavies are generally increased. In contrast, the water soluable substances are reduced rapitly.Except for basswood leaf, the other leavies can immobolize certain mount of nitrogen until reaching the critical points where the nitrogen content of the pine, oak, elm, birch, aspen, and maple leaf is 0.96%, 1.41%, 2.38%, 1.67%, 1.32%, and 1.32% respectively, From the critical points the leavies begin to release mineralized nitrogen: