Abstract: The article reported effects of planting density on wood properties for southern type poplars. Results investigated indicated that: (1) the density had no significant effect on cellular content(%) ; (2)closer spacings would cause fibers to be longer. the distribution frequency of fibers tended to be more homogeneous, but planting density did not seriously influence the ratio of fiber length to its width; (3)the density had obvious effects on micro fibre angles of S2 layer, and close specings would make microfibre angles smaller; (4)with increase of planting density, Crl% would be higher; (5) physical and mechanical properties of the wood were significantly influenced by the density, generally speaking, closer spacings got shock toughness decrease, and air dry density increase. Expect spacing 7 m ×7 m, the density would increase bending strength and elasticity module. Furthermore, planting density has no remarkable influence on crushing strength along the grain.