Abstract: In order to obtain transgenic plants of alfalfa with stronger drought resistance ,dehydrin gene of A mmopiptanthus mongolicus was transformed into the genome of Zhongmu No. 2 mediated by Agrobacterium tumefaciens with alfalfa variety Zhongmu No. 2 as gene transformation receptor. The results showed that the induction frequency of cotyledon and hypocotyls as explant calli was the highest and the best co-culture time for explants and A. tumefaciens was 5 days. 126 resistant plants were obtained. After the identification by PCR and RT-PCR, 11 positive transgenic alfalfa plants were obtained. The elementary phenotype analysis and proline analysis after drought treatment indicated that transgenic alfalfa had stronger drought resistance ability.