Properties of humus and soil structure of five typical dark brown soil profile in“Three Parallel Rivers Area”were studied in the lab and through field survey as well to gain a better knowledge to protect the land resources in the view and provide a favorable basis.Results show that the content of humus and the distribution rule of organic carbon is the same

that is humus layer>leached layer>deposition layer>parent layers.Humin takes the major part in the Humus composition.HA have a higher degree of molecular complexity and chemical stability strong.The degree of soil humus and the complexity of the FA molecules and the chemical stability is the same

with the increase in annual rainfall decreases

followed by Haba Snow Mountain>Qianhu Mountain>Meili Snow Mountain>Yunling>Gaoligongshan.The content of water-stable aggregate are mostly content of 1～0.5 mm diameter

and the size of content and humic acid levels were elevated with the annual average temperature decreases

followed by Gaoligongshan>Meili Snow Mountain>Qianhu Mountain>Haba Snow Mountain>Yunling.Surface organic carbon is related to the content of the 1～0.5 mm size

humic acid and fulvic acid are also significantly related to particle size of 1～0.5 mm

0.5～0.25 mm content.