Abstract: A strain of lactic acid bacterium was obtained from the sample of 40th day natural Fermentation sauerkraut with MRS medium which was special for isolation of lactic acid bacterium. Systematic identification by classical methods showed that the isolated strain was belong to genus of Lactobacillus,Lactobacillus planetarium. Biological characteristic research including measuring growth curve，pH value and acidity of the lactic acid bacterium showed the results that the logarithmic growing peak was 16th hour, the pH value reached at stable levels after decreasing for 20 hours and the high acidity acidproducing series was 20 hours．The results of bacteria inhibition experiment showed that the separated lactic acid bacterium had remarkable bacteriostasis on the growth of E coli and staphylococcus．As the bacterium had the characters of rapid growth，high acidproduction and bacteriostasis，then we can develop the superior bacterium as micro ecological preparation．

Key words: lactic acid bacterium; MRS medium; property of acidproduction