Abstract: Through the sedimentological observations of a large number of outcrops and wells, this study prepared the lithofacies paleogeographic maps of the Ordovician in Ordos Basin in a 3rd-order sequence stratigraphic framework. In the Lower Ordovician, the Ordos Basin was divided into two sedimentary areas (i.e., eastern and western carbonate platforms) by the south-north Yimeng-Central Palaeouplift, where the sedimentary paleogeography was controlled by the North China Sea and the Qilian Sea, respectively. In the Lower-to-Middle Ordovician, the transgression occurred and Yimeng-Central Palaeouplift gradually reduced in the basin. In the Middle Ordovician, the Yimeng-Central Palaeouplift was largely submerged by seawater and divided into two parts, i.e., Qingyang oldland in the south and Yimeng oldland in the north. In the late Middle Ordovician, i.e., the Darriwilian Age (deposition period of the 6th Member of Majiagou Formation), the transgression occurred in the maximum scale. In the Upper Ordovician, the regression occurred, resulting in the vast denuded zones of oldland in the present Ordos Basin with narrow open rimmed platforms and slope facies in the western and southern margins of the basin. In the middle-to-late Upper Ordovician (Katian-Himantian Age), the Ordos Basin almost entirely uplifted to the continent. From Floian Age (the late Lower Ordovician) to Darriwilian Age (the middle stage of Middle Ordovician), i.e., deposition period of the 1st-5th Members of Majiagou Formation, an evaporation environment was formed in vast areas of the eastern basin, leading to the formation of localized lagoon and even gypsum salt lagoon. The western and southern basin was controlled by the development and evolution of Helan Aulacogen and Qinqi Troughs and mainly developed continental margin sediments, which evolved from the carbonate ramps of passive continental margin in the Lower and early Middle Ordovician to the rimmed platform of active continental system in the late Middle and Upper Ordovician.