The root and rhizoma of Rhodiola fastigita S. H. Fu. is a traditional Tibetan medicine used for promoting blood circulation and relieving cough. In recent years, it was generally used as a tonic. So, its chemical constituents were studied. A new flavonoid and six known compounds were obtained. The known compounds were: 4'-methoxyl herbacetin (I), rhodiolin (II), dihydrokaempferol (III), daucosterol (IV), tyrosyl (V) and salidroside (VI). The structure of the new flavonoid was elucidated as herbacetin-8-O-alpha-D-lyxopyranoside (VII), by means of UV, IR, MS, 1H and 13C-NMR spectral data and chemical methods.