Abstract:Two Eucalyptus dunnii provenance-family trials that included 53 families representing 6 provenances at Guilin and Liuzhou in Guangxi, were used to study the genetic variation and genotype by environment interaction for diameter at breast height (DBH) at 8.5-years, and DBH, height, stem volume, wood density and bark thickness at 10.5-years. The 10.5 year results showed: the mean volumes of individual trees at Guilin and Liuzhou were 0.218 and 0.189 m3, the average wood basic densities were 521.0 and 483.7 kg·m-3 respectively; and, the average bark thicknesses at breast height were 1.15 and 1.26 cm respectively. For the 10.5-years growth traits and wood density, there were no significant differences among provenances (P＞0.10), but significant differences among families (within provenances) for 10.5-years wood density (P<0.05). However, there were no significant differences (P＞0.10) at any level for bark thickness at breast height, including no significant genotype by environment interactions for this trait. There were no significant interaction between sites and provenances (P＞0.10) for all the traits except 8.5-years DBH,but significant interactions between sites and families (within provenance)(P<0.05)were found for all the traits studied except 10.5-years DBH. The heritabilities of DBH at 8.5-years and 10.5-years DBH and height were between 0.128 9-0.234 5, the heritability of wood basic density were 0.700 0-0.962 9, bark thickness were 0.105 3-0.335 7.