Based on core observation, cast thin section, well logging data and analysis of sedimentary sequence of the Paleogene and Neogene in the northern margin of Qaidam Basin, Combined with field observations, we studied the sedimentary model in this area. The result shows that clastic rocks are developed in Paleogene and Neogene in the northern margin of Qaidam Basin, such as conglomerate, sandstone and mudstone, and the sedimentary facies are mainly of braided river, braided river delta plain, braided river delta front and shore shallow lacustrine depositional systems. Conglomerate of Paleogene has the characteristic of upright cycle, so it is a water immersion process, and in Neogene it mainly develops alternating deposits of megaclast and fine grained detrital rocks which show frequent hydrodynamic conditions change. Due tothe cyclical changes in precipitation, mudstone developed in megaclast deposit area at the basin margin, and middle-fine sandstone also exsited in the mudstone deposit area at the basin sedimentary centre. This alternatingdeposits ofmegaclast and fine grained detrital rocks can formperfect reservoir-cap combination, and it is favorable for the formation of structural-lithologic reservoir. The sedimentary model shows the process of sedimentary evolution since the Paleogene clearly, which can provide reliable geological evidence for the further oil exploration.