In order to clarify the role of MsWRKY47 gene of alfalfa(Medicago sativa) in regulating salt tolerance in plants, the MsWRKY47 gene was cloned using the cDNA of Medicago sativa ‘WL363 HQ’ as a template, and its protein sequence characteristics and the salt tolerance of MsWRKY47 transgenic Arabidopsis thaliana were analyzed. The results showed that the full length of MsWRKY47 coding region was 1 287 bp, which encoded 428 amino acids and contained a WRKYGQK domain, which belonged to WRKY family and was closely related to homologous protein MtWRKY47 in Medicago truncatula. The expression of MsWRKY47 was the highest in alfalfa roots and could be induced by salt stress. MsWRKY47 was localized in nucleus and had no transcriptional activation activity. The yellow leaf rate of transgenic plants was higher than that of wild type after salt stress, and the oxidative damage was more serious, indicating that the overexpression of MsWRKY47 gene reduced the salt tolerance of Arabidopsis. MsWRKY protein may play a negative regulatory role in the response of plants to salt stress.