Biofilm is a self-protection mechanism produced by microorganisms when exposed to adverse external environment. Most researches focus on pathogenic bacteria and harmful bacteria. Lactic acid bacteria， as important microorganisms in the food industry and human intestinal tract， can better exert their probiotic effects if they are grown in a biofilm state. Extracellular polysaccharides （EPS） are metabolites secreted during the growth of lactic acid bacteria and are the main components of biofilms. The more secreted EPS from lactic acid bacteria， the stronger its ability to produce biofilms. In this study， 41 strains of lactic acid bacteria were isolated in the early stage of the research group， and 10 excellent strains were screened and identified using the high-yield biofilm as an index. Taking a strain of Pediococcus lactis RJ2-1-4 as the research object， the effects of changing the composition of the medium on the amount of EPS were discussed. The optimal medium combination for EPS production by Pediococcus lactis RJ2-1-4 is： 20 g/L glucose， 20 g/L soy peptone， and 8 g/L dipotassium hydrogen phosphate. At this time， the EPS yield reaches the maximum value was （427.83±18.40） mg/L.