Two sesquiterpene lactones were isolated from the flowers of Chrysanthemum boreale Makino by the silica gel column chromatography and recrystallization. On the basis of spectrometric studies including $^1H-NMR,;^{13}C-NMR,;DEPT,;^1H-^1H;COSY,;{13}C-^1H;COSY$, IR and Mass, compounds 1 and 2 were identified as germacranolide, tulipinolide and costunolide, respectively. And they showed antibacterial activity against Vibrio parahaemolyticus, Bacillus subtilis, Bacillus cereus and Staphylococcus aureus. This is the first report that Chrysanthemum boreale contained tulipinolide and costunolide.