Siahu, Sarchahan and Faraghun formations in Fars and Bandar-Abbas regions have been studied with different geochemical methods for evaluated their role in gas generation in the study area. On the basis of Rock-Eval result, Siahu formation in Kuh-e Faraghun cannot be as a suitable source rock because of its low percent of organic matter and high maturation. This formation with shaly lithology has mixed of terrestrial and marine organic matter and deposited in anoxic to oxic conditions. Sarchahan formation only in Kuh-e Faraghun area has a good quality and relatively suitable organic matter. The Study of different parameters of biomarker also shows that Sarchahan formation has deposited in suboxic to oxic condition in marine environment and has shaly-carbonate lithology. Rock-Eval result in well samples indicates that Sarchahan formation only in Kuh-e Siah well has enough qualities and quantities in order to generate hydrocarbon. Rock-Eval and vitrenite reflectance of Faraghun formation also show that this formation in well Kuh-e Siah- 1 is able produce hydrocarbon and can be introduced as the probable source rock of hydrocarbon in this area.