The biochemical composition of some species of Phaeophyceae (Cystoseira): Cystoseira compressa, Cystoseira barbata, Cystoseira elegans, Cystoseira amentacea, Cystoseira barbatula, Cystoseira caespitosa, have been studied. The algal specimens have been collected from Ibn Hani coast north of lattakia in spring 2014. The soluble sugar varies between (13- 56.78%) weight/dry weight [w/dw]. C.amentacea has the highest content of proteins (21.76%), and C.barbata has the lowest (9.51%). Lipid varied between (1.25- 5.55%) [w/dw]. The highest content of ash was in C.caespitosa (31.18%), and the lowest in C.amentacea (23.84%). Iodine was: C.compressa and C.caespitosa (0.68 %), C.barbata (0.69 %), C.barbatula (0.7%), C.amentacea (0.71%), C.elegans (0.8%). Mannitol was within the range (2.91-4%) [w/dw]. Results of biochemical composition of studied species showed the differences between the percentage of values, and this variety affects on the economical value for the species, also affects on the major herbivorous food, that affects on their environment and their community composition.