Abstract: In order to explore the antimicrobial activity and material basis of mulberry leaves extract, the antibacterial activities of 4 fractions (petroleum ether, ethyl acetate, n-butanol and water) from muberry leaves crude extract were tested using micro-plate dilution assay.And the fraction of the strongest antibacterial activity was analyzed by gas chromatography-mass spectrometry.The results indicated that petroleum ether fraction had the strongest antibacterial activity, followed by ethyl acetate fraction, n-butanol fraction and water fraction.Then, the petroleum ether fraction was analyzed by gas chromatography-mass spectrometry.The result showed that this fraction was rich of phytol (24.87%) , cyclo octacosane (18.00%) , hexadecanoic acid (10.20%) , α-linolenic acid (9.06%) , ethyl linolenate (7.92%) , and octadecanoic acid (7.14%) .In addition, it also contained a small amount of α-tocopherol, β-sitosterol and other components.