In this study， the effect of quorum sensing signal molecule AI-2 on EPS production of L. fermentum TG4-1 and P. acidilactici 11-3 was investigated to explore the regulation mechanism of LuxS/AI-2 QS system on EPS secretion of lactic acid bacteria. EPS production and AI-2 activity of strains TG4-1-1 and 11-3 were measured by phenol-sulfuric acid method and V. harveyi BB170 bioluminescence method. The optimal concentration of exogenous AI-2 was selected and the growth， EPS production and AI-2 activity of the strain were measured. The morphology of the strain and polysaccharide after freeze-drying were observed by scanning electron microscopy. The results showed that both strains TG4-1-1 and 11-3 had the strongest AI-2 activity at 10 h， and the highest EPS yield at 22 h， reaching (195.863±1.643) mg/L and (125.179±1.458) mg/L， respectively. After screening， 100 μmol/L exogenous AI-2 was determined as the optimal supplemental concentration of strains TG4-1-1 and 11-3， which had no significant effect on the growth of the two strains at each stage (P>0.05). EPS production of strain TG4-1-1 at 16~22 h and strain 11-3 at 13~22 h were significantly promoted (P<0.05)； meanwhile， the activity of AI-2 was significantly increased at 10 h (P<0.05). After 100 μmol/L exogenous AI-2 was added for 13 h， the cells had smooth surface， regular shape and full shape. However， it had no obvious effect on the surface structure and morphology of exopolysaccharides. These results indicated that exogenous AI-2 at a certain concentration could promote the production of EPS in strains TG4-1-1 and 11-3， providing a certain reference for the mechanism of LuxS/AI-2 QS system regulating EPS.