In this paper, an analysis has been carried out on the problem of the Tertiary Rift Valley Expanding of Bohai Sea based upon gravity-aeromagnetic calculation. Some research results from geothermal heat flow values and the electrical high conductivity layer's upwelling in crust and upper mantle have been referenced in the study. It is considered that there were five big mantle upwellings such as Bozhong, Bohai Bay, Miaoxi, Liaodong Bay and Kenli etc. in the Bohai Sea and its surrounding continent, which formed a group of mantle plumes with clear strike, distinctive shape, big scope and relative assembling character in Cenozoic down warping region of North China due to the deep-seated magma's upmotion.