Truong Sa is an island district of Khanh Hoa province in the south of the East Sea, at the coordinates (7°30 00 -12°0000 N
109°3000114°30 '00"E), including hundreds of small islands with an estimated area of 410,000 /cm2. Truong Sa has not only an important strategic position and large oil and gas reserve, but also high biodiversity degree. Although a lot of studies have been conducted at here but they mainly focused on the marine fauna and flora, the valuable studies on microbial communities that play an. essential role in the natural physical cycle and high application potential are still insufficient. The results of the research on micro-plankton showed that the number of aerobic and fermentation bacteria were high, from 2*10 exponent 2 to 2*10 exponent 5 cells / ml, 0.5*l0 exponent 2 - 5*l0 exponent 2 cells / ml, respectively. The authors also discovered other important groups of bacteria with low number: oil eating bacteria, 07-150 cells / ml
sulphate reducing bacteria, 0-30 cells / ml
Actinomycetes, 00-40 cells / ml
thread fungus, 0-120 cells / mi. No yeasts were found in this study. Five strains of bacteria that produce carotenoid pigment have been isolated and classified into the types of Flavobacterium marinum, Flavobacterium chromogenes, Brevibacterium erythrogenes, Rhodopseudomonas sp. and Flavobacterium marinovirosum.