A totlal of 12 Populus simonii×P. nigra lines (11 transgenic Populus lines and one control line) in 2 years old were used to study the phenotypic variation of tree height(H) and basic diameter(BD) in 6 different sites. The analysis of variance showed that there was a remarkable difference in H and BD among sites (P＜0.01), lines (P＜0.01), and sites×lines (P＜0.05). The average H and BD of transgenic poplar lines ranged in 128-235 cm and 13-24 mm in different sites respectively. The coefficients of H and BD of transgenic poplar lines changed in 19.84%-33.38% and 24.21%-49.16% and repeatabilities ranged in 0.497-0.952，indicating that the variation of poplar transgenic lines was strongly controlled by genetic factors，which were in favor of line selection. Tai model was introduced to analyse the genetic adaptability of poplar lines in different sites. The results showed that except line XL11, other lines grew steady in different sites. Based on the genetic adaptability parameter and the domino effect values of interaction between H and environment, the most adapted site of each line was predicted. Lines XL9, XL1 and XL14 are high biomass and strong stability, which are suitable generalized in 6 different sites.