Abstrcat For studying the reasons of intensive erosion of artificial forest in hilly area of Sichuan Province, the structural properties and its relationship with surface soil erosion ratio are analyzed using soil samples taken from Yanting Agro-ecosystem Station, Chinese Academy of Sciences. The results showed that soil aggregates are very unwaterstable and there are very little non-capillary pores; the waterstable aggregates larger than 0.25 mm, structure ped breaking ration, aggregates mean weight diameter change, and non-capillary pores correspond well with surface soil erosion ratios. The reasons of unstable structure and intensive soil erosion were analyzed. And the countermeas are given briefly