Fiftyfour accessions, including diseaseresistance cotton lines developed in Shaanxi and their descendants, were genotyped to evaluate their genetic diversity and population structure by 72 SSR markers spanning the whole genome of cotton. (1) The genetic similarity coefficient of 54 accessions ranged from 0.733 3 to 0.987 2. Among 1 431 similarity coefficient of pairwise accessions, 11.1% of the similarity coefficient was less than 0.90, 55.6% of the similarity coefficient was more than 0.95. (2) The polymorphic information content (PIC) varied from 0.04 to 0.68 with an average of 0.33. (3) A geneticdistancebased UPGMA cluster analysis revealed that all the accessions could be divided into five groups at cutoff value of 0.877 in the genetic similarity coefficient. Group I included 44 accessions, Group Ⅲ included 7 accessions, and each of the remained three groups included one accession, respectively. (4) A modelbased clustering method (implemented by the program STRUCTURE) showed that all the accessions originated from four clusters. This study indicated that the cotton population, which was comprised of diseaseresistance accessions developed in Shaanxi and their descendants, was characterized by high genetic similarity coefficient, narrow genetic base (genomic ancestry) and poor genetic diversity.