Quaternary polyethyleneimine(QPEI) was prepared via two procedures of macromolecular reactions

tertiary amination and quaterisation

and the antimicrobial properties of this polymeric quaternary ammonium salt were mainly studied by using Escherichia Coli as a disease-leading bacterium.The effects of quaternary degree and pH value on the antimicrobial properties were examined with the method of plate counting living bacterium

and the antimicrobial mechanism of QPEI was studied more deeply via measuring the activities of β-D-galactosidase.The experimental results indicates that QPEI possesses very strong antimicrobial ability

and the antimicrobial ratio can reach 100% when QPEI is contacting with a bacterium suspension of 109 CFU/mL under the conditions of a contacting time of 4 min and a dose of 15 mg/L.The cationic degree of QPEI influences its antimicrobial properties to a great extent

and the higher the cationic degree is

the stronger the antimicrobial activity.In a certain region of pH values

the higher the pH

the stronger the antimicrobial ability is.The results of measuring activities of the enzyme of β-D-galactosidase shows that the antimicrobial mechanism of QPEI is based on a sterilizing bacterium process

and is not only based a restraining action.