Abstract: Arabidopsis response regulators（ARRs） play extremely important roles in cytokinin signaling transduction. As an important forage plant, alfalfa（Medicago sativa） has a prominent position in grass industry and is becoming the research focus of scientific researchers. To investigate the function of the ARR gene, the ARR gene was successfully isolated using RT-PCR technology. The 3302-ARR-3 Flag plant expression vector was introduced into wild-type alfalfa by Agrobacterium tumefacien-mediated transformation, and nine transgenic plants of alfalfa were successfully obtained. Compared with the wild alfalfa type, the transgenic alfalfa had more branches and abnormal number of compound leaves, which provided the original experimental materials for further study of ARR gene function.