Abstract: Using Liquid Submerged Fermentation and the orthogonal experiment design,denitrified biofilm and the contend of the extracellular polysaccharide,the concentration and feeding time were selected.the best concentration of Carbon resource,Nitrogen resource and the optimum concentration of liquid medium was selected.The results showed that the best conditions were the optimal carbon source was soluble starch,the optimal nitrogen source was yeast extract.The optimum proportion of medium is soluble starch2%,yeast extract 0.5%,KH2PO40.3%,MgSO40.05%