Abstract: In order to evaluate the possibility of the ecological risk caused by releasing transgenic trees and the feasibility of applying transgenic trees in forest production,the transgenic Populus simonii×P.nigra with Bt-the spider insecticidal peptide recombinant gene was used as the material.Three kinds of rhizosphere soil microbe including bacteria, actinomyces and fungi were isolated and counted by plate dilution, and the target and resistance gene of transgenic trees were amplified by PCR inbacteria. The result showed that the microbial number in transgenic plants rhizosphere soil was a little more than that in non-transgenic soil after the seedlings planted for seven months. From the antibiotic resistance test, the percentage of the antibiotic-resistant bacteria was 11.58% and 13.00% from two transgenic plants rhizosphere soils respectively, but the non-transgenic plants rhizosphere soil and soil control was only 5.73% and 6.40%, which indicated that the root litter of transgenic poplar could impact on antibiotic resistance of the soil bacteria. The primers were designed according to the target gene and resistance gene sequence of the transgenic poplar, and the PCR reaction was done using genomic DNA of the bacterial clones as the template. The number of bacteria in transgenic plants rhizosphere soils containing the resistance gene increased significantly after planting 7 months. The positive bacteria of the target gene from the soil bacterial clones could be detected in 7 months planting with percentage 2% and 5%, which indicated a possibility that the Bt-the spider insecticidal peptide gene maybe occur horizontal transfer.