Genetic transformation relies on ability to introduce foreign genes into cells. In Agrobacterium-mediated transformation, the sequences between the right border (RB) and left border (LB) of T-DNA are introduced into plant genomes. However, several reports revealed that not only the sequence between LB and RB that was transferred into plant genome. In many case, plasmid backbone sequence may be co-transferred due to the non-recognition of LB by Vir proteins. In this study, the transgenic Dendrobium Sonia' Earsakul possesses antisense CP-ACOI gene was subjected to the analysis of T-DNA border inserted into orchid genome by Adaptor Ligation- Polymerase Chain reaction (AL-PCR) technique. The templates for AL-PCR amplifications were restriction fragments that contained hpt gene and partial T-DNA region with LB included ligated to the AL-PCR adaptors at both ends. Specific primers were designed to be homologous to the sequences of T-DNA and LB region. The sequences analysis of the AL-PCR amplicons revealed that the inserted T-DNA contained an intact LB that linked to the 105-160 bp of vector backbone sequences.