Abstract: In recent years, with the large oil & gas fields discovered, EARS has become a research center received worldwide attention. But at the same time, due to the extremely low level of the research and exploration, the formation mechanism of source rocks and oil & gas accumulation in the youngest rift basin in the world has always been a confusing problem. Through the comprehensive study of geophysical data combined with regional geological data, the author deeply dissected the structural features of the area and its evolution mechanism, and analyzed the fundamental control of tectonic and hydrocarbon accumulation.The study has concluded that the western branch of EARS is the braided tectonic aggregates between the depression and the accommodation zones under the control of pre-existing structure, evolution from north to south is series. Paleo depressions provided the quality environment and enough sediments for the development of source rocks, and pre-existing tectonic accommodation zones provided the advantageous locations for the development of deltas and the formation of fractures and structure traps. At the same time, the pre-existing tectonic accommodation zone controls the dominant direction and the drainage system of hydrocarbon migration. And the hydrocarbon accumulation model controlled by the pre-existing tectonic accommodation zone has been established.Through the above research, it is pointed out that the long axis gentle slope of tectonic accommodation zone is the most favorable exploration direction of the western branch of EARS.