Plum juice was used as material and Lactobacillus Plantarum LP-L134-1-P was used as inoculation strain for malolactic fermentation (MLF) to reduce acids in juice. The effects of the inoculation amount, pH, fermentation temperature, sugar content, and sodium citrates buffer system on deacidification and the growth of Lactobacillus Plantarum LP-L134-1-P in plum juice were studied. The results showed that the total acids increased at the first stage and then decreased during the fermentation. The MLF proceeded normally at pH 3.50 with the inoculation amount of 108 CFU/g. And the bigger inoculation amount was, the more acids were reduced through MLF. When the inoculation amount was increased to 109 CFU/g and pH was 3.50, the MLF could be performed only if the fermentation temperature was more than 25 ℃. It would be easy to perform MLF when the inoculation amount was 109 CFU/g and pH was no less than 3.10. The acidity of plum juice went up with addition of 1.00% glucose, indicating that glucose was prior to convert into lactic acid, thus inhibiting the MLF. In sodium citrates buffer system, the acidity was not reduced, proving that Lactobacillus Plantarum LP-L134-1-P could not use citric acid as carbon resource to run MLF.