Abstract: A comprehensive study of the regional tectonic setting,sedimentary evolution and source reservoir cap conditions indicates that the Gabon Basin has experienced 3 evolutional phases: rifting period,transitional period and drifting period.The sedimentary strata of every evolutional phase are divided into 3 parts: pre-salt sequence,salt sequence and post-salt sequence.The main petroleum systems are the pre-salt and post-salt sequences.The post-salt petroleum system is distributed on the North Gabon sub-basin and pre-salt one is located in the South Gabon sub-basin.It makes clear the main sedimentary distribution of pre-salt and post-salt sequences and their controlment on source rocks and reservoirs.This paper summarizes the main factors of post-salt reservoirs are "reservoir controlled by fault scarp,traps controlled by salt,oil controlled by tectonic and traps" and the main factors of pre-salt reservoirs are "sources and reservoirs controlled by facies,caps controlled by salt,oil controlled by tectonic and traps".