Abstract: Genetic diversities of 19 domestic and foreign alfalfa germplasms were analyzed using ISSR markers. A total of 71 effective loci were obtained for the germplasms using 12 ISSR primers, of which 69 loci were polymorphic, i.e., 96.25% of the total. The mean effective number of alleles(Ne), Nei's gene diversity(H), Shannon's information index(I), and polymorphism information content(PIC) were 1.50, 0.30, 0.46, and 0.33, respectively. The genetic similarity coefficients of the alfalfa germplasms ranged from 0.296 to 0.887, averaging 0.617, suggesting ahigh genetic heterogeneityamong the germplasms. According to a cluster analysis, all of the alfalfa germplasms could be divided into 2 groups at the genetic similarity coefficient of 0.522.One group consisted of 17 germplasms, accounting for 89.47% of the total. Another group had 2 alfalfa germplasms only. A same result was obtained by the principal component analysis. The information could be used for identification and effective utilization of the alfalfa germplasms.