Truong Sa Archipelago is located at the center of the East Sea and it is belonged to Truong Sa district, Khanh Hoa porvince. There are few studies on marine biology e special the marine algae. Results of study on the marine algae at Truong Sa Archipelago showed the variation trends of the geographycal distribution among islands. The highest number species of marine algae is 109 sp. (at Truong Sa Isd.), the lowest number spcecies is is 13 (Toc Tan Isd.) and the average value is 55.8. The homogenous index of marine lagae species among islands fluctuates from 0.10 (Truong Sa and Toc Tan) to 0.68 (Truong Sa and Nam Yet). The number of marine algae species from Truong Sa Archipelago and other areas (Hoang Sa, Philippine and Con Dao) is 34, 57 and 124, respectively. On the vertical distribution of marine algae showed that among 186 species were collected, 130 species found in the tidal zone (occupied 70 percent of total species) and 56/186 species were found in the sub tidal zone (30 percent). In addition, most economical marine algae species distribute in the tidal zone. Besides, the vertical distribution of marine algae also depends on the specific conditions (in the anton, burrows and substrate).