Abstarct: The Zagros oil basin is one of the largest and most important oil basins, which contains huge oil fields due to the presence of regular anticline-syncline structures with a northwest-southeast trend.In this study, the results of Gas Chromatography (GC) analysis, Mass Spectrometry- Gas Chromatography (GC-MS) and Rock-Eval Pyrolysis are used in Pabdeh Formation samples in some oil fields in northern Dezful embayment located at south west of Iran. baxsed on the organic Geochemistry studies, kerogen type, bio-degradation of samples, maturity, depositional environment conditions and hydrocarbon potential of samples from Pabdeh Formation are evaluated. The most samples of Pabdeh formation show the features of kerogen type II baxsed on GC results and the obtained values of pristine and phytoene. The results of Rock-Eval pyrolysis of in Pabdeh Formation samples alsoindicate the kerogen type II and are less than that ofthe II-III mixture. Gas chromatography shows that the origin of organic material of Pabdeh Formation is marine type like phytoplanktons which refers they deposited in an extremely reduced environment. In addition, the results of Gas Chromatography-Mass Spectrometry such as the high ratios of home C34/C35 in the studied samples indicate the relatively regenerative marine environments. The normal carbon values, including C27, C28, and C29, also indicate that the organic materialsforming the samples is mainly originated from phytoplankton and bacteria, with the exception of two samples located near the diatoms range.The star diagrams baxsed on the results of gas chromatography and carbon values C15, C17 and C19 indicate the source of algae and bacteria for organic materials, but the frequency of C25, C27, and C29 represents that the organic materialsoriginated from land plants.baxsed on the results of the gas chromatography-mass Spectrometer and the Hoppan coefficients Ts / Ts + Tm versus the coefficients of regular stranes ratios C29 (29S / 29S + 20R) C29 in Pabdeh Formation samples, most of the samples are in the mature range. The Rock-Eval pyrolysis results of the samples of Pabdeh Formation indicate the beginning of the thermal maturation (oil window) or the end of the diagenesis.Using the results of gas chromatography-mass spectrometry analyzes, the oils type of Pabdeh Formation are most often identified as paraffinic oils, although a number of samples also show naphthenic composition.