Abstract: A new compound, ethyl brevifolincarboxylate(7), along with known compounds scyllo-inositol(1), kaempferol(2), quercetin(3), protocatechuic acid(4), gallic acid(5), kaempferol-7-α-L-rhamnoside(6), ellagic acid(8), kaempferol-3,7-α-L-dirhamnoside(9), brevifolin(10) and corilagin(11), was isolated from Geranium sibiricum L. All the compounds except scyllo-inositol were shown to have a certain degree of antibacterial activity. Corilagin exhibited strong inhibition against Staphylococcus aureus.