|Abstract:As a part of the North China Craton (NCC), the Ordos Basin is located on the western NCC. So far, the study history of the Ordos Basin has been more than one hundred years. And geologists have accumulated fruitful results in its basin basement, lithostratigraphy, biostratigraphy, chronostratigraphy, sequence stratigraphy, lithofacies palaeogeography, tectonic-sedimentary coupling relationship and petroleum geology, respectively. The research degree of the Ordos Basin is becoming higher. Moreover, owing a variety of important energy mineral resource, the Ordos Basin is increasingly brought to the attention of the industrial community. Some basic geological problems, however, are still up in the air, which hamper the comprehensive understanding of the Ordos Basin and even the NCC. These problems including the division, composition, age, top surface of the basement, the early Paleozoic tectonic setting and basin prototype of the west margin of the Ordos Basin, the Ordovician stratigraphic correlation, and the location of the NCC and its history of interaction with the Gondwana supercontinent during the Paleozoic, are controversial, which make the NCC a research hotspot on the international. Another scientific problems related to the marine potash prospecting is: a large scale of rock salt deposited in the Middle Ordovician Majiagou Formation in the Northern Shaanxi Salt Basin (NSSB) in the western NCC, but only potash-containing indicators and local thin potash seams were found in the O2m56 member of the Majiagou Formation. Up to now, a large scale of solid potash deposit has not been found, why? They may also exist in other secondary depression, which has not yet found, of the NSSB. In addition, whether there were some potassium -rich brine migrating out of the NSSB? In order to answer the scientific problems above, we conducted comprehensive research of some classic profile in the southern and western margin of the NCC on petrology, stratigraphy, geochemistry, sedimentology, geophysics and zircon chronology and obtained some new understanding.