Abstract: In this study, Poly-β-hydroxybutyrate (PHB) accumulation was investigated in different growth medium of 11 strain Cyanobacteria and was determined culture medium which yields the more economical for industrial use. These strains were grown in Bristol, BG11 and BG11 modified Allen`s Medium aerated under continuous illumination by fluorescent lamps (3000 lux). Cell walls of the cultures were lysed by ultrasonication and PHB converted to crotonic acid by using sulfuric acid. The amount of crotonic acid was measured by UV spectrophotometry. The yield of PHB produced by the strains according to dry cell weight was ranged between 10.80-65.00% in BG11 medium and 11.89-85.45% in Allen`s medium. In Bristol medium, PHB accumulation is not determined. The highest yield of PHB production (Oscillatoria limnosa 1966/1380: 85.45%) was found in Allen`s medium. Allen`s medium and O. limnosa 1966/1380 is recommended for PHB production.