Abstract: Photosynthehc bacterium strain H3 was isolated from microbial mat of evaporation pond in the saltern of Hainan Island. The absorphon spectrum of living cells showed characteristics peaks of bacteriochlorophyll a and the higher peak of carotenoids.Thin-layer chromatography revealed 5 major photosynthetic pigments including 3 carotenoids with absorption maxima at 485 nm and 516nm, 481nm and 510nm, 486tim and 521nm, respectively in acetone. The total carotenoid content is about 0.6% of dry cell weight An easily solubilized carotenoid - contaning protein has been purified, and SDS-PAGE indicated a single polypeptide of MW 11,000 in the orange protein. A bacceriopnaeophytin is also found. Culture conditions such as light and temperature effect on pigment composihons were examined in photosynthetic bacteria.