Abstract: With the information disclosed by the riverbed bores and field investigation, the exact place of covered Longpan fault was identified in the adolescent valley of Jinsha River. Then the formation mechanism of the old Longpan ramp valley was figured out. In fact, Longpan fault was a reverse slip fault and the Baihanchang fault was a normal left-rotation fault. Due to the different vertical motions of the zones of fracture, the old ramp valley came into being. In the evolutionary period, thick deposits developed in the valley. Through the drill cores, an important phenomenon was revealed that the deposits had a well-regulated layered fabric and multi-type components. The regional geology shows that the layered deposits was a result of different sedimentary environments and the disparate components accorded very well with the corresponding new tectonic movements such as periodic mountain raising and glaciations in middle Pleistocene in this region.