Abstract: A Pinus massoniana plantation of Danjiangkou reservoir of Hubei Province was selected as object to analyze the stand features under different regulation density from three respects of the stand structure, natural regeneration status and biodiversity.The results showed that average tree height, average DBH, dominant height, and under branch height were significantly increased with the stand density decreased. At the same time, the height distribution in three densities of Pinus massoniana plantation all showed a normal distribution curve, but the stand height structure at low density tended to be more complete. In high density stand, small diameter class trees were main components, but in lowmedium density stand, the number of larger diameter tree was increased significantly. The number of regeneration species under forest of high density, medium density and low density P. massoniana were 5, 7 and 8, respectively, and the dominant regeneration species were Quercus variabilis and Rhus chinensis. With the stand density increased, the number of regeneration seedlings, the ratio of saplings and seedlings to dominant trees gradually decreased. The seeding characteristic was more concentrated in height ≥ 50cm, and the stand was lack of low age old seedlings. The density decrease of Pinus massoniana stand promoted the increase of biological diversity of understory vegetation in some extent, but there were some differences on the variation trends of biological diversity between different layers.