The capsular polysaccharides-producing Lactobacillus strain isolated from traditional fermented products was used in this study. Using Lactobacillus plantarum C88 as an original strain for treatment with nitrosoguanidine and screening with negative staining, the capsule-de?cient mutant strain was obtained, it was named L. plantarum C88M3. On the basis of the results of 16S rDNA sequence analysis, growth test and RAPD analysis, compared with the wild type strain C88, the mutant strain C88M3 showed the difference in genetic characteristics and capsular polysaccharide production. In this paper, a capsule-de?cient mutant strain was obtained by inducing mutation methods, and the results of this work would provide further insight into the function and mechanism of probiotic action.