Two partly modified insect-resistant genes (BtCryⅠ Ac gene ［Bt gene toxin against Lepidopterean insects］ and API gene ［arrowhead proteinase inhibitor］) were transferred to the triploid hybrid of Chinese white poplar ((Populus tomentosa Carr.×Populus bolleana Louche)×Populus tomentosa Carr.) mediated by A. tumefaciens. An examination was made concerning the survival of Agrobacterium in transgenic plants during the process of transplanting and subculturing on the nutrient medium. Results suggested that 80% of plants, which we got by repetitious selection on media added with 50 mg/L kanamycin and 300 mg/L carbenicillin showed positive reactions after examination with molecular methods. The ELISA test indicated that the Bt toxoprotein was expressed in 7 of the transgenic sub-clones. Leaves, stems and roots of all the 28 transgenic plants were cultured on the YEB medium added with 50 mg/L kanamycin and the survival of Agrobacterium was detected in 3 sub-clones (33, 37, 5) which could have existed for 24 months in the bottle. Those 3 transgenic sub-clones were transplanted and cultivated for one month in the room, and then the target Agrobacterium was found in rhizosphere of the sub-clone 33.