在美洲黑杨×小叶杨新无性系木材密度性状遗传变异及相关分析的基础上，开展木材密度性状幼－成相关及早期选择研究。单性状总平均木材密度（ρｃ）最佳早期选择林龄为５～６年，早期选择的遗传增益为８７２％～９７１％，早期选择的年效率为１５２１７％～１４１３０％。多性状指数法早期选择的最适林龄为第５年；构建指数的主要性状为总平均木材密度（ρｃ）、年轮密度（ρｒ）及早材密度（ρｅ）等３个木材密度性状；在第５年应用最佳选择指数Ｉ＝２２７９１ρｃ＋１１０８８ρｒ＋１１５８９ρｅ进行选择时（ｉ＝２０６），早期选择的遗传增益为０１１４２ｇ／ｃｍ３，比成熟期第１０年单性状直接选择的遗传增益高１５１６５％。 Based on the genetic variation and correlation analysis of wood density traits of Populus tomentosa × Populus simonii clones, we studied the relationship between young-formed wood density traits and early selection. The best early selection age for single-trait total average wood density (ρc) was 5-6 years. The genetic gain of early selection was 872% ~ 971%. The annual efficiency of early selection was 15217% ~ 141. 30%. The optimum selection index for multi-trait index was the fifth year. The main index of construction index was the density of three woods, including the average wood density (ρc), annual ring density (ρr) and early wood density (ρe) In the fifth year, the best selection index I = 22791ρc + 11088ρr + 11589ρe was selected (i = 206), and the genetic gain of early selection was 0.1142g / cm3, which was more than the direct selection of single traits at the tenth year of maturity The genetic gain is 151.65% higher.