To explore the possibility of expressing the hybrid peptide CAD in the alfalfa, Medicago sativa, the cDNA sequence encoding CAD was obtained by recursive PCR(rPCR), and fused with elements such as Ω sequence, Kozak sequence and KDEL sequence to improve the expression level in the transgenic plants, and cloned into the plant transformation vector pCAMBIA1390R. This recombinant plasmid was transformed into Agrobacterium tumefacien LBA4404 and CAD gene was transformed into alfalfa by A. tumefacien-mediated method. The regenerated alfalfa plants were selected on medium 20 mg/L hygromycin. The results of PCR and Southern blotting showed that the CAD gene was successfully inserted into alfalfa genome. Proteins extracted from transgenic alfalfa showed a certain bacteriostatic activity to Salmonella and Staphylococcus aureus.