Monoacyl maltitols were synthesized from maltitol and four fatty acids( lauric acid,octanoic acid,oleic acid and stearic acid) by NOV435 lipase-catalyzed method.High purity of monoacyl maltitols was obtained by silica gel column seperation and semi-preparation HPLC.The inhibition rates and minimum inhibition concentration( MIC) of monoacyl maltitols against bacterials and yeast at 0.062 5 ~ 6 mg/mL were investigated.The resultsshowed thatmonoacyl maltitols possessed excellent antibacterial activity,strong inhibition against Bacillus subtilis and Streptococcus mutans,good inhibitory effect on Eschericheae coli,and depressing against Yarrowia lipolytica to some extent.Among the monoacyl maltitols with differentfatty acidacyls,mono lauroyl maltitol presented the strongest antibacterialability, mono octanoyl maltitol and mono oleoyl maltitol took the second,and mono stearoyl maltitol had relatively weak inhibition activity.The MIC of mono lauroyl maltitol against Eschericheae coli,Bacillus subtilis and Streptococcus mutans were 2.0 mg/mL,0.5 mg/mL and 0.25 mg/mL,respectively,which had the better antibaterial activity compared to mono lauroylmaltoseand mono lauroyl sucrose.