26 wild accessions and 2 cultivars of whip grass (Hemarthria compress a (L. f.) R. Br.), which collected in the fields of Sichuan Agricultural University (SAU), were used to study on their ploidy level and reproductive characteristics. The results showed that there were 4 tetraploids (14.3%), H028, H029, H052, H053, chromosome numbers were 2n=4x=36, and 24 hexaploids (85.7%), 2n=6x=54. There was no significant correlation between geographical distribution and ploidy level in this research. From 2006 to 2008, hexaploids set few seeds, but all of the tetraploids set some seeds more or less. H052 had the highest seed set (11.22%). The tetraploids had potential for seed production, especially H052, it should be possible to obtain hybrids by cross-pollination in the future.