Abstract: Abstract：Beijing plain, located at the junction of the Yanshan Mountains and the North China Plain, consists of sea facies, lacustrine facies, and alluvial sediments. Due to its complicated characteristics, traditional geological survey methods are not applicable in this area. In order to get high-precision information of geological structure in Beijing plain, this paper presents a new practical survey method, whose principles are as follows: first, the entire alluvial-proluvial fan is subdivided into several subsections based on geological structures and sedimentary features; after that, new high-resolution geological cross sections are created by using framework borehole data, geophysical data and historical research results; and then, the characteristics of Quaternary sediments in each geological element is well described; finally, the 3D geological model of Quaternary is built by using computer techniques and the GIS system of Beijing plain. This model can play an important role in city planning and construction and also promote the development of hydrogeology, engineering geology and environmental geology in Beijing.