Abstract: In combination with the method of residual strata thickness and 3D interface recognition method of geophysical prospecting,the palaeogeomorphic map of Pre-Jurassic has been established.There are two major water systems and several secondary water systems developed in the study area.The south one is the tributary of the secondary ancient river,namely Qingxi River,which is into the Qingxi River from southwest.While the north one is also the tributary of Qingxi River and into the Qingxi River from southwest to north.The microtopography can be divided into 6 kinds of paleogeomorphology units,namely valley landforms,ridges,valleys,highland,mound and flood plain.The research results show the Palaeogeomorphology basically controlled the reservoir distribution and structural form of lower part of Yanan formation.The incised role of the ancient valley not only shortens the contact distance between Yanan formation and oil source layer,but also provides preferential migration pathway for hydrocarbon.