Four new flavone C-glycosides, luteolin 6-C α- L-arabinopyranosyl-7-O β- D-glucopyranoside (1), apigenin 6-C β- D-galactopyranosiduronic acid (1→2) α- L-arabinopyranoside (2), luteolin 6-C β- D-galactopyranosiduronic acid (1→2) α- L-arabinopyranoside (3), and luteolin 6-C β- D-glucopyranosiduronic acid (1→2) - L-arabinofuranoside (4), along with three known ones, were isolated from the leaves of Lophatherum gracile. The structures of the new compounds were elucidated by extensive spectroscopic methods as well as acid hydrolysis. All the flavone glycosides isolated from this plant were screened for their in vitro antiviral activity against respiratory syncytial virus (RSV) with cytopathic effect (CPE) reduction assay, and several flavone 6-C-monoglycosides showed potent in vitro anti-RSV effect.