Abstract: Diatoms are the biofouling organisms that live on the underwater biofilm in the light reachable depth. The extracellular polymeric substances (EPS) is an important factor for diatoms adhering on the surfaces and plays crucial roles in biofilm formation and development. The methods to extract the soluble EPS and the bound EPS are different and no accredited extraction methods available for the bound EPS until now. In this study, the components of the bound EPS of benthic diatom Amphora sp. were studied with four different extraction methods including water bath treatment at 30℃ and 70℃, formalin-sodium hydroxide treatment and cationic exchange resin treatment. The results showed that the main components of bound EPS varied generally with the extraction methods, among which the range of DNA content changed the most, the next were protein, sugar and uronic acid, the least was sulfonic acid. The extraction efficiency by low temperature water bath was relatively low while high temperature water bath might have negative influences on the subsequent EPS analysis. The cationic exchange resin treatment showed a good extraction efficiency but it caused serious damages to cells. The method of formalinsodium hydroxide treatment gave a balanced and efficient result as the extraction derived the highest total EPS especially for sugar and uronic acid and less serious damage to the cells.