Cymbidium mosaic virus (CymMV) is the most prevalent pathogen affecting seriously to economic value, quality and productivity of orchid. Triple gene block proteins (TGBps) and coat protein (CP) play an important role in controlling CymMV movement between cells and long-distance movement in the host plant. In order to supply initial information for generating CymMV-resistant orchid varieties, in this study, the authors designed two RNAi hairpin structures and evaluated the efficency of these vectors in silencing target viral genes using the plant model Nicotiana tabacum. The first vector PK7WIWG2(II)-CP contains gene coding coat.protein and the other PK7WIWG2(II)/0rf2-4+CP contains genes coding for coat protein and triple gene block proteins, both of them were put under the control of the CaMV 358 promoter. These genes were transformed in tobacco leaves through Agrobacterium tumefaciens. After selecting by kanamycin antibiotic, the authors obtained 45 CP transgenic tobacco lines and 38 orf2-4+CP transgenic tobacco lines. Based on polymerase chain reaction (PCR), The authors selected 26 transgenic lines for each vector. The artificial injection result showed that both 10 transgenic lines randomly selected and wide-type control had no clearly inoculative symptoms. Whereas Reverse transcriptionPCR (RT-PCR) result illustrated that RNA CymMV was present in wide-type control but not in transgenic lines. Hence, the authors concluded that two structures investigated could be efficiently resistant to CymMV in tobacco.