Miscanthus floridulus is a species of the genus Miscanthus Andersson, which has attracted worldwide interests as one of the most potential bioenergy crops. In this study, the genome size of M. floridulus was determined by flow cytometry using rice (Oryza sativa L. var. Nipponbare) as an internal reference. The average genome size that resulted from 6 collections of M. floridulus was about 2596.59 Mb, namely 2 C DNA = 5.31 pg (1 pg=978 Mb).