The shrub plant, Cotoneaster wilsonii Nakai, endemic to Ulleung-do of East sea in Korea is considered a rare plant. Distribution of genetic variation and ecology were investigated in two populations (only total 84 individuals) using 13 allozyme enzymes to better understand its population biology and to comment on management proposals relevant to this species. Measures of genetic variation in this species were lower than values reported for species with similar ecological and life history traits(ca. 15% of loci polymorphic within populations, 1.21 alleles per polymorphic locus, and 0.42 expected heterozygosity, respectively). A total of 17 putative loci were scored, but only three loci were polymorphic in at least one population. We examined all patterns of genotypes from these two populations where nine and seven genotypes(11 genotypes from all 84 individuals) were detected. We have applied the IUCN Red list criteria to this species based on this current inventory. Since C. wilsonii in Korea was treated as an endemic (sensu strido) or a synomized taxon to central Chinese species, C. multiflorus (sensu lato), we applied these sensu lato (sh and sensu stricto (ss) concepts to this taxon. C. wilsonii(ss) were evaluated as Critically Endangered(CR), while C. multiflorus turned out to be Least Concern(LC) due to the abundant individuals and wide distribution in central China. The current population genetic structure was probably a result of a population bottleneck at colonization or the result of local extinction of intervening populations and the small effective population size with the recent human disturbance. The mating system of Cotoneaster is known largely as apomixis. The lack of diversity we found within populations is consistent with genetic bottleneck, especially combination with the evidence for apomixis. More speculative possibility,