In this study, the authors examined diversity and activities of some actinomycetes isolated from mangroves in Giao Thuy, Nam Dinh province. The distribution of artinomycetes in soil is strongly affected by external factors. Extra-cellular enzyme producing ability of mangrove a.ctinomycetes is very high, particularly the ability of producing cellulase degrading filter paper (122/128 strains), CMC (110/128 strains), protease (83/128 strains) and amylase (78/128 strains). Mangrove actinomycetes often produce antibiotics of narrow activity range, few strains are able to produce broad ranged antibiotics.