An experiment was performed to study the inhibition effect of Lactic acid bacteria on the growth of Escherichia coli O157:H7. When L.casei subsp.cacei, L.plantarum, L.fermentium, Lactococccus lactis and L.helveticus were respectively mixed with E.Coli O157:H7 ATCC43895 and cultured,each of the 5 strains of Lactic acid bacteria had no inhibitive effect on the survival of E.Coli O157:H7 ATCC43895. When E.Coli O157:H7 ATCC43895 was inoculated into the 24 h-old Lactic acid bacteria MRS culture, the E.Coli O157:H7 ATCC43895 lost all its activity. The low pH(pH4) adjusted by lactic acid had substantial inactivating effect on Escherichia coli O157:H7. The study showed that the acidic metabolites of Lactic acid bacteria inhibited the activity of Escherichia coli O157:H7.