Abstract：This paper analyzes in detail the characteristics of sandstone dikes in outcrops and cores in the Late Triassic Yanchang Formation in the Ordos basin and preliminarily elucidates the formation mechanism and evolutionary process of the sandstone dikes. The unconsolidates fine sands deposited in the early stage were liquefied in the late stage in response to earthquakes, and meanwhile with rapidly increasing pressures inside sands, the liquefied sands were injected into the fissures in surrounding rocks very quickly, thus forming sandstone dikes. According the above-mentioned analysis, combined with the tectonic setting, the authors think that sandstone dikes acted as conduits for oil migration and also exerted a certain influence on the formation and destruction of oil accumulations.