Abstract: Taking the new root tips of six Hemerocallis cultivars such as ‘Mighty Chestnut’ as test materials, the ploidy identification and karyotype analysis were carried out by conventional chromosome pressing method, which provided a theoretical basis for the taxonomic, cytological and breeding studies of this genus. The results showed that ‘Mighty Chestnut’ and ‘Lilly and petals’ were tetraploid (2n=4x=44), ‘Flore Pleno’ were triploid (2n=3x=33), ‘Paprika Flame’, ‘Forty Second Street’ and ‘Qu Xian Huang Hua’ were all diploid (2n=2x=22). The chromosome types of six Hemerocallis cultivars mainly include m, sm and st; The karyotype was 3B except for ‘Mighty Chestnut’ which was 2B. The chromosomes of ‘Paprika Flame’ and ‘Forty Second Street’ had satellite, and the rest had no satellite. The chromosome length ratio of the six Hemerocallis cultivars ranged from 2.01 to 2.44, and the karyotype asymmetry coefficient ranged from 64.55% to 71.86%.