This paper studies its regional tectonic evolution and characterizes the cross actions to illuminate the forming processes of the Bengal Basin. It is suggested that this basin has undergone four stages: the prerift-synrift, continental drift, soft collision and hard collision. According to the tectonic evolution and the current tectono-sedimentary characteristics, the Bengal basin is divided into six secondary tectonic elements: west shelf, shelf slope, north depression, south depression, central uplift, and east Fold belt.Studies of the evolution processes show that the remnant oceanic part of the Bengal basin came into being in the Paleocene, and began to shrink from Eocene. In Pliocene,the eastern part of the remnant ocean basin vanished because of the plate convergence,and the remnant ocean was confined to the southern basin. The remnant oceanic part of the Bengal Basin exerts a key control on the distribution and migration of the deposition center as well as the hydrocarbon distribution.