Abstract: To clarify the genetic diversities of major tobacco cultivars in China, 24 tobacco cultivars were selected for whole-genome scan with 430 K tobacco SNP array. The genetic diversities of the 24 cultivars were analyzed. The results showed that 103 133 polymorphism (SNP) loci were found, which basically covered tobacco genome. The genetic similarity of the 24 cultivars ranged from 0.308 6 to 0.997 7. The 24 cultivars were classified into different groups by UPGMA analyses to reveal their genetic relationships. It indicated that SNP array could identify the diversity at whole-genome level, which could be used to analyze the genetic diversities of different cultivars. Very narrow genetic background was observed for major tobacco cultivars. Thus, it is an urgent task to introduce diversified germplasm resources into tobacco breeding program for increasing tobacco genetic diversity.