Psammosilene tunicoides W. C. Wu & C. Y. Wu, belonging to the monotypic genus Psammosilene in the family Caryophyllaceae, is an endangered and endemic plant to China. A karyological study was carried out on 20 populations of P. tunicoides across its distribution region. All populations of the P. tunicoides studied are diploid (2n=2x=28), and the basic chromosome number was confirmed to be x=14. Various chromosome morphologies were revealed, but didn’t show clear geographical pattern. P. tunicoides is initially placed in Silene L., but P. tunicoides is different from Silene L. in the basic chromosome number of x=10 and 12. The results of this study support the view that P. tunicoides is turned into the independent genus from Silene L. Combining the available chromosome studies of Saponaria L. and Psammosilene tunicoides, the two species have relatively consistent chromosome diversification with a basic number of 14, and most species of the Saponaria L. contain diploid individuals, which suggested that there are certain phylogenetic relationships between Psammosilene tunicoides and Saponaria L.