The Gabon coastal basin is the passive margin basin whose sedimentary cover includes the Cretaceous, the Paleogene and the Neogene. The sedimentary strata are divided into three parts: pre-salt strata, salt strata and post-salt strata. According to the exploration status, post-salt petroleum system is mainly located in the north of sub-basin and pre-salt petroleum system in the south of sub-basin. The paper compares the two sub-basins in the fields of the geology background, petroleum geology parameter, size and the exploration potential. The research result is that the key for the south sub-basin exploration is trap identification and the key for the north sub-basin exploration is sand prediction.