Abstract: In order to explore the development and utilization value of a newly screened L. reuteri LT018 strain from centenarians,this study first tested the viable cell count and bacterial vigor of the strain in the process of continuous culture for 300 generations,and judged its genetic stability. The survival rate and agglutination rate of the strain in the simulated gastrointestinal fluid were measured to determine the probiotic characteristics of the strain.Further,this strain was combined with traditional Lactobacillus bulgaricus and Streptococcus thermophilus fermenting agent to prepare fermented buffalo milk.Based on the single factor experiment,the optimal process was explored by response surface experiment.The results showed that the viable count and bacterial viability of L. reuteri LT018 were maintained at a high level during the continuous culture for 300 generations;The survival rate of the strain in the simulated gastric juice and intestinal juice was higher than 99.07% and 77.83%,respectively,while maintaining the agglutination rate greater than 55.4%.The optimal preparation process of fermented buffalo milk was:Lactobacillus reuteri starter:traditional starter 2:1,white sugar was added 3.00%,fermentation temperature was 40.00℃,and the sensory score of fermented milk was the highest(86.63±1.47),the number of live bacteria of Lactobacillus reuteri also reached 1.033×10⁸ CFU/mL.This study provided an important theoretical and technical reference for the development and utilization of this strain.