Abstract: In order to find new antimicrobial substance, antimicrobial activities of 70%(volume fraction) ethanol extract of Eucommia ulmoides Oliv. leaves and its fractionated extracts were tested. The result showed that ethanol extract and ethyl acetate extract had inhibitory effect toward bacteria and fungi, while ethyl acetate extract had particular inhibition behavior toward A. flauus and A. niger. Butylalcohol extract and aqueous extract had inhibitory effect toward bacteria, but no had inhibitory effect toward fungi. Petroleum ether extract had scarcely inhibitory effect toward bacteria and fungi. The maximal inhibition diameter was above 10mm, the minimum inhibition concentration was between 0.25%-3.0%. The extracts of E. ulmoides leaves had good thermostability on antimicrobial activities. Inhibition rate gradually increased with time, but hardly changed after 16h.