Studies of the genetic relationship could provide reference for the excellent germplasm innovation and new varieties breeding. Within this study, we investigated the genetic diversity by SSR markers using capillary electrophoresis fluorescence detection technology, in 187 accessions that include cauliflower, broccoli, Roman cauliflower, landraces and wild species. A total of 313 alleles were amplified from 30 pairs of SSR primers, with an average of 10.43. According to the curd phenotypic characters of the materials, these genotypes were composed of four subgroups: cauliflower (subgroup 1, P1-81), broccoli (subgroup 2, P82-147), Roman cauliflower (subgroup 3, P148-154), wild and local species (subgroup 4, P155-187). The narrowed genetic diversity was observed among subgroups 1, 2 and 3, except subgroup 4 that showed abundant diversity. The phylogenetic tree and population structure analysis assigned these genotypes into three groups. Cauliflower (G1) and broccoli (G2) were grouped independently, while Roman cauliflower together with wild species and landraces assembled the third group (G3).