Abstract:The Lactobacillus plantarum KF5 was isolated from Kefir grains（Tibet，China），which could secret exopolysaccharises（EPS）during the growing process.The initial yield of EPS was 49.32 mg/L with phenolsulfuric acid method.The conditions for the synthesis of EPS were optimized with single factor and orthogonal experiments.The optimum conditions were as follows：the incubation time 30 h，the initial pH of medium 6.3 and the inoculum volume 3%.Moreover，initial pH of culture medium and inoculum volume had no significant effect on the yield of EPS，but the culture time had significantly influence on the production（p<0.05）.The yield of L.plantarum KF5 could reach 95.58 mg/L under the optimum conditions，which was higher more than 26.48%before orthogonal optimization.