Abstract: In order to explore the ploidy level and genome size of Sorbus sect. Sorbus species, the nuclear DNA content from somatic cells was measured by flow cytometry and Oryza sativa subsp. japonica ‘Nipponbare’ was used as the internal control. The results showed that the genome size of 19 species ranged from 0.648 to 0.803 pg, with the diploid, triploid and tetraploid levels, including 15 diploid species with 2C values ranging from 1.335 to 1.607 pg for, and one triploid species S. himalaica with 2C values of 2.137 pg,and three tetraploid species, S. albopilosa, S. prattii and S. pseudovilmorinii, with 2C values of 2.594, 2.891 and 2.751 pg, respectively. The 2C values of 16 species and new ploidy levels of five species were reported for the first time, indicating that there were changes of ploidy heterogeneity among interspecific and intraspecific in Sorbus sect.Sorbus.