Abstract: Heterosis of wood quality characteristics among 18 Populus × xiaozhuania cv.‘popularis' improved clones has been studied and group-average method of clustering was used to cluster the P. × xiaozhuania cv. ‘popularis' improved clones according to genetic distance. 1.Significant heterosis was observed for wood quality characteristics among P. × xiaozhuania cv.‘popularis' improved clones in fiber length,fiber width, ratio of length to width,double) wall thickness and wood specific gravity. 2.18 clones were clustered into 5 groups. The first group included clones growing fast with medium fiber quality. The second group included clones with medium growth,small wood specific gravity and better fiber quality. The third group included clones growing fast with good fiber quality. The fourth group had only one clone P15A,which grew fast and had better fiber quality. The fifth group included one clone which had the biggest wood specific gravity, medium growth and better fiber quality. 3.4 supper clones were selected according to multiple comparisons heterosis analysis,cluster analysis and resistance.