Using the stress related transcriptional factor gene,DREB2A,as the target gene,and the herbicide tolerance resistant gene,bar,as the selective marker,a plant expression vector,pCD2A,was constructed.Transformation was performed via the Agrobacterium-mediated method on the alfalfa cultivar ‘Gongnong No.1’ using the cotyledons for explants.After co-culture,bacteria restraining and selective culture,71 resistant regenerated plants were obtained on the medium with 2mg/L Basta.A further selection on leaves of the resistant plants,11 positive plants were obtained by PCR,which indicated that the gene DREB2A has inserted into the genome of the plant.