RAPD analysis was applied to assess the genetic relationships among 32 accessions of watermelon [Citrullus lanatus (Thunb.) Mansf.].Fifteen primers(2.08%) were screened from 720 arbitrary 10-mer primers,and a total of 104 bands were amplified, 43 of which (41.35%) were polymorphic.The average number of DNA bands amplified by each primer was 7.0.A dendrogram was constructed by using complete linkage method.The 32 accessions were assigned to six groups which were one East-Asia group, one American group,two medial groups and two African wild groups.Each ecological type group had its specific bands which were available to discriminate other groups.The results obtained by RAPD analysis were fundamentally identical with their origins and characteristics,and the genetic diversity in watermelon was narrow.