Abstract: Since the Neogene,the ancient Songhua-Liao River system have undergone several changes with the alternation of fluvial and lacustrine formation on a large scale.In the early Miocene, ancient NenJiang-West Liao R. formed a centripetal interior drainage; and in the Late Miocene, Daan-Dabusu Lake and Panshan-Tienzuang tai Lake were formed.During the Pliocene, a fluvial and lacustrine climax had reached ever since the cenozoic time Subsequently, in the Tai-Kang Stage,the hydrographic not had become centripetal interior drainage once more.At the end of the early Pleistocene or the early stage of the Middle Pleistocene, Songhua R. had cut through the divide near the neighbourhood of Shanxing, and sabsequently the Liao R.also had cut through the Tieling-Faku Hill.Thus the centripetal interior drainage of the ancient Songhua R.Liao R. become the recent exterior drainage.