Abstract: Using MRS media,one strain of lactic acid bacteria was isolated from milk. The strain could present Gram-positive,catalase-negative,non-spore,and produce lactic acid. The 16 S r DNA gene similarities(99.7%)between strain AR66 and its closest phylogenetic neighbor, Leuconostoc mesenteroides, were higher than those previously reported within the leuconostoc. So strain AR66 was identified as L.mesenteroides. Strain AR66 had the free radical-scavenging ability. Three free radicals-scavenging ratios of strain AR66 were positively correlated with bacterial density,respectively. At a concentration of 5 ×108CFU/m L,the scavenging ratios of intact cells on hydroxyl radical and superoxide radical were 49.76%,and 83.33% respectively,which demonstrated obvious higher than intracellular extract. However,at the same concentration,intracellular extract had better DPPH-scavenging effect(scavenging ratios 77.09%) than the intact cells. In addition,strain AR66 for 60 h had the ability of cholesterol-reducing(removal rate,44.73%). The study had important meaning to the exploitation of probiotic health.