The genetic diversity of 35 germplasm resources of yam from different places and areas were analyzed by ISSR molecular marker and the primary core collection was constructed by Least Distance Stepwise Sampling.The results showed that:(1)12 primers selected from 32 random ISSR primers which amplified 142 loci including 97.18% polymorphic loci.The average of Shannon information index (I),Nei’s genetic diversity (h),effective number of alleles (N_e) and number of alleles (N_a) by POPGENE 32 analysis was 0.423 0,0.269 4,1.427 1 and 1.971 8 respectively which indicated there was highly genetic diversity in these 35 yam resources.(2)The clustering result of analysis by NTsys2.10e software showed that the genetic similarity coefficient ranged 0.54-0.97.Some materials distributed in different origins and far geographic distance showed high genetic similarity coefficient in 35 accessions.(3)The percentage of polymorphic loci was reduced although the change of Shannon’s information index and Nei’s genetic diversity was not clear with the samples reduced in six samplings.The bank of core collection from No.4 sampling was most representative in six samplings whose sampling number was 31% of the initial sampling and the percentage of polymorphic loci was 97.8% before sampling.