Abstract: Through the analysis of oil shale samples of the 7th Member of Yanchang Formation, and combined with geological features of Triassic sedimentary period of oil shale in the south of Ordos Basin, it is believed that the rich oil shale of the 7th Member of Yanchang Formation was formed affected by paleoclimate, structure, and sedimentary environment.Warm and moist paleoclimate is conducive to improving the initial productivity of lakes in the sedimentary basin. At the sedimentary end of the 8th Member of Yanchang Formation, volcanic eruption events occurred on the west and southwest margin of the basin led to the formation of the sedimentary pattern dominated by deep lake of the sedimentary period of the 7th Member, which was favorable for enrichment of organic matter. Tuff bed generated from tuff particles produced by volcanic eruption at the bottom of the 7th Member of Yanchang Formation could insulate oxygen and be conducive to oil shale preservation. Oil shale developed in deep lake sedimentary environment is the thickest and has higher oil content, and is semi-deep and shallow lake facies. It indicates that the thickness of oil shale in the 7th Member is obviously controlled by sedimentary facies.

Key words: oil shale, Triassic, geological features, enrichment regularity, Ordos Basin