通过调查马尾松中龄林的生长情况，对其群体遗传变异进行分析。结果表明，马尾松两广优良家系中龄林存在丰富的遗传变异，树高、胸径、材积和冠幅等性状在家系层次上有极显著或显著差异，这些差异主要由遗传因素制约，各性状受中度、中低度遗传控制。主成分分析表明，树高、胸径和材积为主要生长性状，它们的累积贡献率达89.54%。采用Structure Version 2.2软件进行群体遗传结构分析，将群体分成5大类，在第4组群中，广东的家系数量最多，且组群生长性状值最高；第2组群中广西的家系数量最多，而生长性状值仅次于第4组群。

Through investigating the growth of middle age of Pinus massiana forest, the genetic variation of population was analyzed. The result showed there were abundant genetic variation and very significant or significant differences among families of Pinus massiana in height, diameter breast-high, volume and crown, moreover, the differences were mainly controlled by genetic factors and these growth traits were genetically controlled in medium or lower level. Principal components analysis showed that height, diameter breast-high, volume and crown were principal components, the cumulative proportion of these three principal components achieved 89.54%. Using software Structure Version 2.2 to analyze the genetic structure of population, all families were divided into 5 groups. The group 4, including most families of Guangdong, had the most growth traits. The group 2, including most families of Guangxi, the growth traits was next to that of the group 4.