Abstract: Actinobacterial species diversity and population characteries of rhizosphere soil of six seagrasses species of the Gulf of Mannar Biosphere Reserve India was studied using Kuster’s agar (KUA) and Actinomycets Isolation Agar (AIA) for the first time. Higher population density was recorded in the, Halophila sp. rhizosphere soil (67×102 CFU g–1) and the lower density was recorded in Syringodium sp. rhizosphere soil (24×102 CFU g–1) in Kuster’s agar. Whereas in AIA medium, higher population density was recorded in the Halophila sp. and Thalassia sp. rhizosphere soils (49×102 CFU g–1) and the lower density was recorded in the Syringodium sp. rhizosphere soils (38×102 CFU g–1). Out of the 59 strains, characteristically distinct 30 strains were selected for further taxonomic identification based on the morphological and good growth characterization. On the basis of spore mass colour, reverse side colour, aerial and substrate mycelia formation, production of diffusible pigment sporophore morphology and examination of spores by using SEM results all the 30 isolates were taxonomically identified as different species of Streptomyces.