The lithofacies palaeogeography map can show the pattern of basins and mountains and the characteristics of original deposition. The map of MongoliaGansu-Qinghai area revealed lots of different sizes sedimentary basin groups formed in early Cretaceous in study area. These basins often belonged to extension rift basin, received lacustrine-fluvial deposition of Lower Cretaceous due to extensional tectonics movement of early Cretaceous. The sedimentary environments and situation of lithofacies palaeogeography of early Cretaceous are favorable for hydrocarbon. The source rocks were mainly distributed in sub-depression of Northern Qilian-Alashan fault depression Group. The source rock is a set of grey and grey to dark calcareous mudstones of lacustrine, which were controlled by lacustrine depositional system (shallow-moderate-deep lake). Besides, the distribution of source rocks were dominated by the climate belts, dry in south and moist in north'.