Abstract: In order to investigate the mechanism of extracellular polysaccharide (EPS) synthesis in Lactobacillus plantarum, a strain of Lactobacillus plantarum YZH81 with high EPS production was selected for the study of extracellular polysaccharide synthesis gene cluster (cps). After whole-genome sequencing, alignment and analysis, it was determined that the genome of YZH81 contained two cps gene clusters, one of which (cps1) had yet to be identified in terms of structure and function, while the other (cps2) was highly homologous to other reported Lactobacillus plantarum strains. The conclusions in this study, the cps1 gene cluster resulted 52.28% reduction in EPS production, accelerated self-aggregation, reduced adhesion and 32.42% reduction in the ability to generated 1,1-diphenyl-2-trinitrophenylhydrazine (DPPH·) in the YZH81∆cps1 strain compared to the wild-type YZH81 strain. The results suggested that the cps1 gene cluster of strain YZH81 was associated with EPS synthesis and established favorable conditions for further studies on the mechanism of EPS biosynthesis in this strain.