The distribution of O-glycoside hydrolase (fucoidanase, polymanuronic lyase, laminaranase) in 84 species of marine invertebrates in Vietnam was studied. After collected, species names of the invertebrates were identified and samples were kept at 4°C during transfering to the laboratory. The digestive tracts, hepatopancreas, crystalline stalks and eggs were separated, homogenenised in a buffer and then, concentrated to obtain a crude extract. The crude extracts were applied on a Sephadex G-25 column (1.2 x 20 cm), then enzymological activity was screened with substrates from brown algae, including fucoidan, polymanuronic acid and laminaran. It was shown that O-glycoside hydrolase was widespread in the animals analyzed. Some mollusks, annelid and echinoderm species such as Lambis sp. (gastropoda), Septifer biocularis, Maleus maleus.. .(bivalvia) could probably serve as sources of enzymes that degrade polysaccharides from seaweeds as well as O-glycoside hydrolase.