A system for obtaining regenerated plantlets of "double low" Brassica napus by using cotyledonary petioles as material was established. The turnip mosaic virus coat protein (TuMV-CP) gene inserted in the binary vector pBTu in the Agrobacterium tumefaciens LBA 4404 was integrated into Brassica napus through co-culture of cotyledonary petioles with LBA4404, and the material in co-culture was selected under the stress of Kanamycin. Regenerated plantlets were obtained, and the specific TuMV-CP gene was proved to be integrated into the genomic DNA of the regenerated plants by the specific PCR amplification, dot hybridization and Southern blot. All these transgenic plants were proved to be resistant to virulent TuMV by virus challenge in different degree.